We usually pack for 5-7 days no matter how
long the cruise. I have no problem spending an hour or so doing laundry in the self serve laundromats. I either go back to the cabin, bring a book or just chat with the other people doing their laundry.
I'm not worried about wearing the same things; really, how much attention do you pay to what other people are wearing? Right now my DH is sitting just across the room and I can't tell you what he's wearing (except that it's shorts and a T shirt