Well, we know Stan isn't very concerned with hygiene:Is Stan's underwear notable dirty vs whatever Lena and Louise running around?

his room is notably dirty, something that gets mentioned a few times and he acknowledges it. So i doubt he pays more attention to the state of his clothing.
Man, I'm trying to throw loser Stan a bone here and empathize a bit with this pityfull social awkward nerd not being able to be on good terms with his two dramatic room-mates.