I think that every time your wife sneaks me into her bedroom.
Seriously tho, mine too. She weighs 10 lbs less than when we got married, eats well (and cooks great, those things are related), and works out like a fiend (I work out a lot as well, although not quite as fiendishly). Wears a size 2 or 4 depending on the brand.
When I look back on my life I can think of a bunch of dumb things I've done, but I hit the lottery in picking a wife who aged well. If I could bottle up the formula and sell it I'd be a trillionaire. Best I can say is that a woman needs the right amount of vanity. Enough to want to look good, but not so much that she spends an hour putting on makeup to go to the gym.