Jen said something strange this morning. She claimed that if I were to put on a clean pair of underwear (boxers mainly) before bed, then I’d need to put on a new pair in the morning after my shower. Now, I no longer officially support wearing the same pair of underwear for more than 24 hours (though I accidentally had some boxer briefs stay on for the night shift last night), but 8 hours for a pair of underwear is pretty extreme to my masculine sensibilities. Interestingly, according to her, it would be OK to change them every morning, even though it would include the same 24 hours worth of stresses as changing them every night. In her defense (since she’s adamant about reading this before I post it, so as to ensure that I don’t elucidate her personal underwear replacement theories), she does have a consistent rule: always switch underwear after a shower. I think if my underwear were all up in my business instead of hanging loosely, I might be more inclined to agree. As it is, since I’m a good environmentalist, I don’t want to waste water*.
*Even if water is infinite (as claimed in comments somewhere recently), they still make me pay for it. Communists.
Thoughts?
By the way, Jack Bauer gets tortured 4 times every 24 hours while chasing gunmen, snapping spines, and probably sometimes being submerged in tanks of urine. Think he changes his underwear? Not when the fate of the free world is on the line.
Words 
I’m with Jen on this one. You sweat a lot when you sleep (or so says your mother). Therefore, the underpants must be changed in the AM.
Count me in with Jen and Bethany. Always change in the AM and ALWAYS after a shower. TOTALLY WORTH any wasted water!!!!
I think if you’re in a line of work that requires an after work shower every day, you may as well commit to being a nighttime showerer, never take morning showers, and go to work in whatever boxers you slept in.
If your day doesn’t lead to a scenario where you need a shower at the end of the day, but you work in an office and are a morning showerer, the nighttime shower is really terrifying for precisely this reason.
I say one night of sleep is worth about 3-4 days of actual day time wear. So in the summer months, maybe you lay out a pair of boxers to wear ONLY AT NIGHT, up to four times.