Unlike your milk, your sunscreen, and your driver's license, your fragrances don't have a hard-and-fast expiration date. One scent might be past its prime in six months. Another could still smell amazing after ten years. Perfumer Linda Sivrican of Capsule Parfums gave us four freshness rules to follow.

1. Perfumes with heavier base notes last the longest—and can even get richer (in the best way) over time. Oriental scents, like Yves Saint Laurent Opium and Calvin Klein Obsession, are prime examples. "They contain strong woody notes, such as patchouli and vetiver, which improve with age," says Sivrican. Citrus, green, and floral scents don't last as long because they are lighter and tend to evaporate more quickly—consider buying those in smaller bottles.

2. Direct sunlight and heat break down a fragrance. And any setting that fluctuates in temperature—like the inside of your car or the bathroom—is a death sentence. The best place to stash perfume is away from light in a dry, cool place. "Storing a fragrance in a lingerie drawer, a cabinet, or even the fridge will preserve the ingredients and precious oils," says Sivrican. (If you choose the fridge option, just remember to keep the perfume away from food that easily absorbs odors, such as butter.)

3. Another enemy of perfume? Air. "It causes ingredients to get contaminated and the perfume to oxidize," says Sivrican. Make sure caps are on tightly and, if you want a travel-friendly option, choose a solid perfume over a rollerball. "The wax in a solid binds the ingredients and perfume oil together, extending the shelf life significantly," says Sivrican.

4. If you tend to have a lot of fragrances in rotation, choose ones with a higher alcohol content—they'll last longer (both in the bottle and on your skin). Look for eaux de parfum and avoid essential oils, which are diluted with a smaller amount of alcohol (or none at all).

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