There are no laws saying that you have to wear fresh clothes every day. and I'm pretty sure that people that people who live in the woods and hermits don't change their boxers/panties every day either.
Currently I'm wearing boxers that i wore for work, then out for dinner and now im sleeping in them. I plan to wear them tomorow and if i still havent done any laundry by that time then I'll wear them another day probably. Do you wear fresh clothes everyday?