A. Just to give you an idea of how imaginative (or you might, less generously, say ignorant) I was about fragrance before I took this job, I thought you could lay down a perfume the way you lay down a good wine, and it would mature to become a more delightful version of itself when you opened it for, say, your granddaughter's bat mitzvah. Afraid not, says Ellen A. Molner, executive perfumer at Givaudan Fine Fragrances. The ingredients break down with time and exposure to light (natural or artificial) and heat, so if you want a perfume to remain fresh, store it in the fridge.
Bottom line: An unopened bottle of fragrance is good for 12 to 18 months, though a light scent—such as a citrus, one with fresh green notes, or a delicate floral—will most likely begin to turn sooner.