This is a great thread 
I typically am a 1 ride per shorts girl, but have reused shorts where the ride I just did was relatively short. Like, if I ride 15 miles and don't get all sweaty then they're "safe" to me, though it grosses me out a little if I think about it too much. Don't ask me why, maybe I'm a little of a germaphobe.
But after a longer ride, forget recycling them. I have also used the wash in the shower technique, typically on RAGBRAI where no washing machines are available and you have to pack somewhat light for the week.
"Only the meek get pinched, the bold survive"