I recognized early on in life that life, in general, is more exciting when you have a crush on someone. It means you'll always have someone to sigh over when girl talk is going on and that you'll always have something to make your heart flutter a bit, whether it be from daydreaming for hours on end or seeing the person in the actual flesh. Even if nothing real materializes out of your little crush, at least you had something fun to think about every day.
So I've made it an effort throughout my life to make sure that there was always a guy to plant my thoughts on. I've had crushes that have spanned years, and I've had crushes that took me by surprise, consumed my thoughts for two weeks nonstop, and then evaporated without warning. And I have to say, those two-week crushes are the most fun. They allow you to indulge yourself in ridiculous fantasies for a few days without the risk of being disappointed or getting hurt.
Of course, two-week crushes are good, innocent fun if you're single, but I don't imagine they are particularly healthy when you're already in a real relationship.
However, we're all human, and I highly doubt that even those with strong marriages don't stop to admire a delicious human specimen every now and then. Or even to casually stalk their celebrity crushes on the internet (that's how I found out that Chris Pine was an English major and has the same birthdate as Harry Potter).
This crush-seeking habit I've got is probably going to be a hard one to break once I find my ultimate crush, but you can't make me stop having fun with it while I'm still wild and free.