Every time I wash my dishes, I face the eternal question: Am I making my plates more dirty by using this week-old sponge? Perhaps my dining ware gets dirtier than average, but sponges seem to go bad about 3.4 minutes out of the package. But, what am I, a millionaire? I can’t go buying new sponges every other day.

Though it’s great (and environmentally friendly) to try to clean and reuse sponges and other household products, some of them just can’t be sanitized. For example, an old kitchen sponge holds about 82 million germs per square inch, according to a study published in Scientific Reports. And don’t even bother with the old “zap it in the microwave” trick. The study also found that regularly sanitized (via microwave, boiling, and bleach) were just as contaminated as never-cleaned sponges.

Does that mean every sponge is one-and-done? What about loofahs, razors, and other limited-use products? To answer these questions (and stop potentially spreading E. coli all over my dishes), I asked cleaning and lifestyle experts to find out how long we can use these household items before they need to go. Luckily, most things don’t need to be thrown out immediately, though there are a few items that’ll need to take a quick trip to the garbage can.

Kitchen Sponges

Now that we know sponges are a hotbed for dangerous bacteria, how often do they need to be replaced? Emily McCrary-Ruiz-Esparza, the brand editor at House Method, suggests trusting your nose. “Kitchen sponges should be thrown out as soon as they smell anything but neutral,” she says. If you’re still not sure, McCrary-Ruiz-Esparza suggests replacing them every one to two weeks.

For a longer-lasting kitchen cleaner, you have a couple options, according to Leanne Stapf, vice president of operations at The Cleaning Authority. First, you can use a microfiber sponge. “If you clean your microfiber sponge regularly, you could get one to two months of use before it will need replacing,” Stapf says. So while they’re more expensive, they last more than twice as long as the typical sponge.

Second, you can use a plastic dish brush. “The bristles of dish brushes tend to shed moisture faster than sponges, meaning they don’t develop as much bacteria and bad odors,” Stapf says. “They’re also very easy to clean!” Put the brush on the top rack of the dishwasher and wash with the rest of your plates. And if you don’t have a dishwasher, wash the brush with hot water and soap and use a fork to pick out errant food particles. Also, you should sanitize these brushes by soaking them in distilled white vinegar once a week, according to Stapf. With that kind of care, the kitchen brush will last one to two months.

Now, that’s way too much work for a clean-aphobic person like myself, but as long as you throw out your kitchen cleaning items when they start to smell and never go past two months of use, you should be fine.

Dish Towels

Dish towels can be a real cleaning danger zone. They’re a great alternative to using paper towels, which reduces waste. But they also live in a bacteria hotbed, and it’s easy to forget these little towels when you’re lugging your laundry to your building’s one washing machine.

First of all, you probably need to wash your dish towels more frequently than you currently do. “Dish towels see a lot of wear and tear, which is why they need to be cleaned so regularly,” Stapf says. “As often as every other day!” Oh, boy. I barely wash my own body every other day, let alone my dish towels.

Still, just as with sponges, dish towels usually stay damp and are exposed to harmful germs like E. coli and salmonella—so they’re a bacterial breeding ground. In addition to washing the towel three to four times a week, you should replace them as soon as they get damaged. Though Stapf doesn’t have an exact timeline for the trash, she says “once spots and stains become visible following a wash, that’s when you know it’s time to toss it.”

Bath Towels

I once had a bath towel that got so dirty and gross-smelling, no wash could possibly fix it. When it came out of the drier still semi-hard from general crud, I had to let it go. Now, this was in my poor, New York City-dwelling days when I had to haul 60 pounds of laundry down to a laundromat that always smelled vaguely of ammonia and BO. So… try to keep your disgust at bay.

But what if you’re not a garbage person? How long do bath towels last with regular washing? So first off, your bath towel is still probably filthy (sorry). If you want to take a trip to Vomit Town, read Business Insider‘s rundown of all the terrible bacteria growing in your towel right now. According to the article, you should wash the towel after every three uses to avoid a colony of germs using your towel as their home.

But even when you keep up a twice-weekly cleaning regimen, the towels won’t last forever. Stapf recommends applying a similar rule to dish towels—if it starts to get threadbare or worn, throw it out. Basically, if it doesn’t feel absorbent, let it go. Usually, bath towels are made with sturdier materials, so they’ll last longer than their kitchen cohorts. Luckily, that means a towel can last about two years (as long as you aren’t a super gross-o like me).

Bath Mats

First of all, remember that you can wash your bath mat in the washing machine along with the towels, Stapf says. Yes, they often have that weird plastic-y, rubber stuff on the bottom, but it won’t melt or bend in the wash. And bath mats don’t need to get cleaned every three days. Instead, every one to two weeks is fine, according to Stapf.

Only every two weeks? Bath mats are suddenly my new favorite thing. Still, they will lose their absorbency, much like towels do—so when that feeling goes (usually in about two years or so), get a new one. Again, this can vary based on the type and quality of bath mat, so trust yourself: If it makes you sad to look at your bath mat, treat yourself to a new post-shower rug.

Loofahs and In-Shower Washcloth

“No matter your preference, these shower items need to be replaced every three to four weeks,” Stapf says. That’s not too surprising, since their only job is to clean dirt off your body, then sit in a hot, wet, steamy room.

Before you toss these aside, Stapf says it’s best to clean your loofahs and washcloths with soap and hot water at least once a week—and to try to let them dry out as much as possible. If they never fully dry, mold will form, and that’ll cut their lifespan in half.

Razor

Shaving with an old razor is not only unpleasant, but it’s also possibly dangerous. “When razors are constantly exposed to water, rust could appear, which means you will have to change the blade right away,” says Marieta Ivanova, cleaning and home improvement expert for Fantastic Cleaners Brisbane. If you cut yourself with a rusty blade, you have a greater risk of infection. Though it’s not likely you’ll get tetanus from a rusted razor, it could happen. And even if you stay perfectly healthy, shaving with a dull blade just plain sucks.

Ivanova suggests throwing away your razor if it has any trace of rust. If there’s no rust, it really depends on how often you use the razor to know how long it will last. Sadly, there are no hard-and-fast rules here. Ivanova says that when a blade starts to pull or tug at the hair, then its time is over. If you have coarse hair that you shave every day, that could happen in a week. If you shave less than weekly, the blade could last a month or two.

All in all, pay attention to how the blade feels. If it doesn’t run smoothly over the skin or doesn’t seem to be removing as much hair as it once did, then you should probably bust out the replacement.

Toothbrush

The American Dental Association has a pretty hard-and-fast rule for dental tools: Toothbrushes (or toothbrush heads for electric versions) need to be replaced every three to four months. Get rid of the brush even sooner if the bristles are frayed or misshapen.

Recently, a dentist asked me how often I replaced my toothbrush. So start throwing these out more often (or get ready to add them to the list of things you lie to your dentist about).

Hairbrush

I still have a hairbrush from fifth grade. I don’t know why. It’s nothing special, but it seems a shame to throw it out when it still technically functions.

Stapf does not recommend this kind of brush hoarding. “Residue and natural oils often build up on the bristles of your brush, so it’s important to clean it twice a month.” Over time, this gunk and oil can’t be properly cleaned and often the bristles lose their effectiveness. “Depending on usage, brushes last from six months to a year.”

Excuse me for a moment… I suddenly have a lot of brushes to throw away.

Makeup Brushes/Sponges

“Makeup brushes can trap dead skin cells, dirt, and oil from your face and residual makeup within the bristles, creating a breeding ground for bacteria if they are not cleaned regularly,” Stapf says. Ah, there’s an infection waiting around every corner.

Fortunately, makeup brushes are easy to clean and don’t need to be replaced that often. Just clean them at least every week (for well-used brushes) with a mild soap, let them dry completely, and you’re safe!

According to Stapf, the bristles will tell you when to dispose of the brushes. If they start to fall out, lose their shape, or feel hard, throw them away. This can sometimes take a year or more to happen, so your favorite brush shouldn’t have to head to the trash any time soon.

For makeup sponges, you have to be a little more careful. Still clean them at least once a week, but it’s even more important that they dry completely. It’s easy to let a damp makeup sponge live in your bag for a couple of days, and that’ll bring about mold and germs.

If the sponge smells bad, let it go. If it still feels absorbent and applies makeup properly, then it should be safe to use. Just keep it dry, soap it up from time to time, and you should be able to use for about three months.

Plastic Water Bottles

It’s not a good idea to reuse the Aquafina bottle you impulse-bought in line at the grocery store for very long. Though the rumors about cancer-causing chemicals leaching into your water via plastic bottles was debunked, disposable bottles aren’t meant to be cleaned. Since your mouth + water = bacteria, bottles need to be thoroughly cleanable to avoid germ overgrowth.

But what about sturdy, reusable bottles? Sadly, like so many things in our lives, they’re also filled with germs. A small study from Treadmill Reviews (not quite Johns Hopkins, but it looks fairly legit), found that every type of reusable plastic bottle was full of bacteria. For some, they were as bad as licking your dog’s chew toy.

Plastic is tough because it can quickly form small cracks and cuts that hide bacteria. If you clean your bottle every day, without scratching the interior, the bottle should be safe to use for a few months, according to Ivanova. But, really, it’s better to throw the plastic bottle away and opt for a stainless steel version. Those are scratchless, easy to clean, and make a cool dinging sound when you tap them. The dinging sound isn’t of great importance, but it does give me a weird joy.

With diligent cleaning, a lot of your household items can live a fairly healthy life. But whenever a product starts to fade, tear, or smell unseemly, the best thing to do is get it out of your house and kiss that bacteria goodbye.

Amber Petty is an L.A.-based writer and a regular contributor to Greatist. Follow along as she shares her weight-loss journey in her new bi-monthly column, Slim Chance. Take singing lessons from her via Sing A Different Tune and follow her on Instagram @Ambernpetty.