Beauty supplies can get expensive — your favorite tube of lipstick might cost more than you’re willing to spend on coffee in a week, your straightening iron can easily cost as much as your weekly groceries, and that perfect nail polish color often comes as a splurge. Their cost, and sometimes our love for a particular product, makes getting rid of them particularly difficult. But, just like most anything you buy, your favorite products eventually just can’t be used anymore and can even become harmful to put on your body. So, when is it time to let go? Here’s your guide:

Mascara & Eyeliner 

Bad news: the life of your mascara and eyeliner isn’t all that long. If it’s an opened mascara or eyeliner more than six months old, it belongs in the trash, no matter how much you have or haven’t used it. After around three months, liquid eye products start to gather bacteria that can irritate or give you an eye infection. No amount of makeup will cover that — you’re best off ditching these after six months. If you’re a pencil eyeliner gal, those last about three years.

Powdered Makeup

Good news! Your eye shadows, mineral makeup, and the like have a good shelf life. Powders, pressed or loose, stay good for around two years.

Liquid Foundation

Another long-lasting beauty tool, your liquid foundation is good for anywhere from six months to two years depending on the product. You’ll notice changes in the color and structure when you apply it as it starts to break down — toss it when you start to notice these changes. If your makeup has been sitting out in sunny spots, it’s likely to break down faster. If you’ve got a foundation (or any makeup) that you really love, be sure to keep it somewhere cool and out of direct sunlight.

Lipstick

Lipstick is oil-based, making it less of a bacteria breeding ground than water-based cosmetics. But, after a year or two, even natural oils start to go bad. There are no negative side effects, but your lipstick has gone bad when it no longer goes on smooth or tastes a little strange when you apply it.

Nail polish

Nail polish begins to separate and break down after about a year. Anything you’ve got that is nearing or past that expiration date that you haven’t been frequently using should go. The good thing? Trendy nail polish colors seem to change every season, anyway.

Sunscreen

An important part of any beauty regime, sunscreen usually lasts about 6 months to 1 year. Over time it can destabilize and lose SPF power, so be sure to switch this important product up every 6 months to a year so you’re getting adequate protection from the sun.

Shampoo and Conditioner

These daily (or every few days!) essentials can last up to two years. If it becomes too runny or starts to separate, it’s time to chuck it.

Body Lotions

You’ve got about two years with your favorite lotion. Nothing bad will happen if you continue to use the product after two years, but it becomes less effective the longer it sits on a shelf. Best to replace it every couple of years.

Makeup brushes

To maintain your brushes, make sure you wash them in a mild detergent every two to three months. If you’re not washing them, they can get weighed down with makeup and bacteria and should be thrown out after a few months. If you’re regularly cleaning them, these guys can last a long time. You’ll know they’re ready for the trash can when the bristles start falling out often, the original consistency of the brush is gone, or they start to smell bad.

Straightening Iron

Straightening irons usually last several years and, thank goodness, for their cost and many benefits. Few mornings are worse than the one where you turn on your straightening iron only to find it’s not heating up — you’ll know when your straightening iron has retired. What many people don’t take into account is cleaning their irons. Gunk can easily build up and lessen the effect of the iron or lead to singed or smelly hair. Cleaning your straightening iron every few months with a simple hydrogen peroxide and baking soda solution or a product from a beauty supply store is a great idea to prolong its life and preserve your hair.

It’s hard letting go, but purging your old beauty products isn’t just a great excuse to buy new ones, it’s also a way to be sure your products are actually doing what you bought them for in the first place.