I'll wear the same pair of pants up to three times ( although I don't keep count ). A trout probably a time or two - unless I'm doing something that would cause them to get nasty quick ( like mowing the lawn ).
Being truthful - if I don't feel like it and they aren't dirty, I'll wear the same bra/panties the next day but never over that. O_o Seriously. If all you did was sit on your bum all day posting at EoFF you aren't really doing anything to stain them. ( Exception to all those with bladder control and streak mark problems. XD! )