In my 600-piece perfume collection, there are just two scents that I save for extra special occasions. I cherish each spritz and carefully consider when to wear them. Or, I did, until one of them went bad. I was completely thrown off the last time I misted myself. Instead of the typical confidence-boosting honey aroma wafting to my nostrils, I was greeted with a screeching metallic odor that was so foul I needed to scrub it off immediately. In that moment, I realized my perfume had expired, and I wished I had worn it more often instead of letting it collect dust on the shelf. Just like makeup and skincare, perfume also has a shelf-life, but the specifics aren’t as clear-cut as other cosmetics. TL;DR, Some fragrances can last for decades without expiring—it all depends on the notes and how well you take care of your bottle. So, how can you stop your perfume from expiring? Below, two fragrance experts share key signs that your fragrance has expired, as well as tips to get the most out of your perfume so you can enjoy it for years to come. How do I know if perfume has expired? There are a few ways to tell if your perfume has gone bad, but a colour shift isn’t one of them—despite what many perfume content creators say. Your nose is always the best judge. “The biggest sign your perfume has expired is a scent change,” says Kelly Kussman, founder of fragrance brand Cayla Gray. Essentially, if your perfume “smells sharp, sour, metallic, overly alcoholic, or develops a vinegar-like quality,” there’s a good chance it’s gone bad. (TBH, it’s disappointing when this happens, but who wants to smell like any of those things?) So what if your perfume has changed colour and still smells pretty good? In most cases, it’s still safe to wear. “Some fragrances naturally deepen in colour over time, especially vanilla-heavy or amber fragrances,” adds Kussman. If the colour changes and your perfume smells rancid, that’s a clear sign that it’s expired, and it's time to toss. How long does a bottle of perfume last? Berenice Watteau, perfumer at DSM-Firmenich, tells Cosmopolitan that there’s no clear-cut lifespan of perfume. “Its longevity depends on the fragrance composition and how it is stored.” Some perfumes can last for decades if they’re kept away from light and heat fluctuations. “I have a 30-year-old Marc Jacobs perfume that I still wear and still has the same nostalgic smell,” Kussman shares. The notes in your perfume can oftentimes determine how long it will last. “Generally, citrus-forward fragrances tend to expire faster, while deeper woody, amber, resin, musk, and vanilla fragrances often last longer,” says Kussman. This is because lighter notes degrade and fade faster, whereas heavier notes naturally have more longevity. Regardless of the notes, though, your perfume will maintain its gorgeous smell for years if you keep it away from heat and light. (I’ll give you some more details on this later.) How long does perfume last unopened? Again, there’s not a set amount of time that a perfume will last, but if it’s unopened, it will maintain its integrity and aroma for much longer. But remember, perfume is meant to be worn! It shouldn’t be collecting dust in the corner of your vanity—unless you have it there solely for decoration. How can I prevent my perfume from going bad? There are a few simple steps you can take to ensure your perfume smells ~incredible~ for years to come—and it all comes down to how you store it. Heat and light degrade perfume, so Kussman says it’s extremely important to keep your bottles out of direct sunlight, and to avoid storing them in the bathroom where temperatures constantly fluctuate. A cool, dark place—like a cabinet, drawer, or closet—is the safest place for your ‘fumes. Watteau also suggests keeping perfume in the fridge to “help preserve freshness and slow down fragrance molecule breakdown,” though that’s not totally necessary.