Exactly how many products to buy at a beauty sale so that you don’t waste in the long run

It’s that time of the year: People are Marie Kondo-ing their makeup bags, opting out of fancy dinners in order to save money, and making room in their beauty cabinet. Because it’s summer sale season, baby.

My head’s practically spinning (with heart eyes, mind you) with all the sales going on RN. There are summer sales at practically all of your fave stores, and then, coming up is the Christmas of them all: Amazon Prime Day. What I’m eyeing? All of the beauty finds, at a fraction of their regular cost. These are exciting times, y’all.

That said… have you ever filled your bag (or cart) so freakin’ much that, come six months later, some items are still just sitting on your shelf, unopened and collecting dust? Same. Majorly. Sometimes your heart is bigger than, well, the square footage of your skin (and apartment), and you can’t just use every single product that you hoard. In the Herculean effort to make sure we shop beauty product sales with a strategy—no penny or product wasted—I consulted a pro to see just how much you should really buy when the prices are slashed.

Here’s the deal—regular skin-care products typically have a relatively long time of use. “For beauty products such as a moisturizer or anti-aging product, adhere to the expiration date for anything that has been opened and already exposed to air,” says Rachel Nazarian, MD, board-certified dermatologist with Schweiger Dermatology. “If it hasn’t been opened and has been stored in a cool and dry location, I allow using for eight to 12 months after expiration.” So you can get a good amount of skin care, but try not to be too extra with what you score. Also, make sure you’ve got your foundational products. “Cleanser, both gentle and exfoliating, a moisturizer, and a night cream—it’s good to restock on these when you can, but always be mindful of expiration dates,” adds Dhaval Bhanusali, MD, a New York-based dermatologist.

On the other hand, it’s also a good time to try those skin-care actives you haven’t gotten around to yet. “This would be a good time to take a chance on some antioxidants, like vitamins C and E, and even things like sheet masks or eye patches and see what works and what doesn’t work since it’s at a lower price point than normal,” says Dr. Bhanusali. “The rule should be to try a new product for four weeks—at two weeks, you’ll know if you can tolerate, and at four weeks, you’ll know if it’s helping.” His pro tip? Take progress pictures to see how it’s really affecting your skin. “It’s also good to grab some spot treatments for acne here to have when in a pinch,” he says, pointing to ingredients like benzoyl peroxide or salicylic acid, or even pimple patches.

If you’re on the market for SPF, keep in mind that these actually have a shorter shelf life. “I’m a little bit more stringent [with sunscreen] because they’re less stable than other products—especially chemical sunscreen—and I allow for them to be used up to six months past the expiration date if they’re stored in a cool and dry place,” says Dr. Nazarian.

Something you can go nuts on buying? Soap. “Soap, such as bar soap, typically has a stable and long shelf life,” says Dr. Nazarian. “That’s where consumers should stock up.” Make room in your carts, folks.

This can also help you out—here’s how many skin-care products you actually need for your “skin-care wardrobe.” And these are companies that give back, so you can shop and feel even better about it.