I just wanted to pass along this article, which quotes Guy Robert. There's no news here, nothing to get in a tizzy over, but these are good points to bear in mind. Oxidation of perfumes is without a doubt a serious issue to consider when buying and owning fragrances over long periods (years, or even decades). Air in the bottle will change things, ever so subtly at first, but given enough time and a combination of other natural factors, like temperature, humidity, and exposure to sunlight, will eventually ruin the perfumer's idea, and create a fragrance very different from that which he formulated.