In my experience with skincare routines, I’ve learned that accumulating too many products without understanding their shelf life can be costly and ineffective. The little jar symbol with a number followed by an 'M'—known as the period after opening (PAO)—indicates how many months a product remains effective after being opened. For example, if it says '12M,' it means the product is safe to use for 12 months after first opening. Many people assume that unopened skincare products can last indefinitely, but this isn't true. Even unopened items have expiration dates, especially if they contain active ingredients or are classified as drugs, like acne treatments. These expiration dates might not always be clearly printed on the packaging, but it’s important to check and be mindful. Collecting skincare products just because they look appealing or are on sale can lead to having many items that eventually expire before you can use them all. This can cause your investment to go to waste. Instead, I recommend focusing on a consistent, simple routine with products that suit your skin type and needs. Rotate products carefully and prioritize those with shorter shelf lives. Moreover, if you notice a change in the product’s color, texture, or smell, it’s a good sign it’s time to discard it, even if the PAO suggests it should still be usable. Expired products can cause skin irritation or reduced effectiveness, which defeats the purpose of skincare. Ultimately, understanding product expiration and the period after opening helps you save money and maintain healthy skin. I find that keeping a small, manageable collection aligned with my skincare goals prevents clutter and ensures I’m always using fresh, effective products.