Most younger people don't know this, but most women lose all of their libido after menopause. I'd be willing to bet that there's not a single man in the US about to tie the knot that knows that lifetime monogamy will likely involve nearly two decades of celibacy.
Kind of sheds a whole new light on the mid life crisis and middleaged men who cheat, like General Patreus. Most of those guys have gone without sex literally for years before they finally crack.