just out of curiosity. never thought of it before. i can't even make up a poll cuz i have no idea how often this should be done! or is it just "use your own judgement" and use until it's ratty, then they become rags?
this question occurred to me as i was thinking about my towels from college... it seems it wasn't that long ago i bought them (well, 5.5 years) and they were all pretty and new, but now they're my crappy, would-almost-use-them-while-dying-my-hair towels!