So, I'll admit to:
Boxers: 20 hours +/- 2 hours.
T-shirts: 45 hours +/- 4 hours.
Jeans: 70 hours +/- 5 hours.
Say average day of wear is 14 hours (8am - 10pm).
And here's a link on a survey I found on habits being looser than assumed:
So how about you guys?