My commute is 9 miles each way (about 30 minutes each way) and I'm in TX so yeah, I sweat.

I use the same (tight) bike shorts for AM and PM and will use the same pair for a couple days before I wash them. I only have 2 pair of good bike shorts and commute ~4 days/week so I'm kind of stuck in that respect.

Would be nice to get another pair or two so I can be squeaky clean when I take off every morning but does it really matter if I'm going to be sweating in 5-10 minutes anyway? Nope.