If you're a true denim aficionado then you'll only wash your jeans once every other blue moon, and then with such a brief dip in cold water that it's barely worth it.
I'm less fussed about my trousers than my other clothing. Suit bottoms go on rotation and get dry cleaned every week or two. Jeans get washed when they get dirty and not before. Pretty much everything else gets washed immediately, but I don't have a particular problem of sweaty legs and rotting groin.