I chose every week, but it's not like we have a schedule for changing them or anything. I mostly change them when I happen to have spare time to do a load of laundry, and I guess that it averages out to be about once a week. Holy cripes-- to change on with every bath, for every person, that would be sometimes 35 towels a week, and more if we have guests. I only OWN about ten towels, and I'm already doing 16 to 17 loads of laundry a week. If I had to wash that many towels, I'd never have time to actually TAKE a shower, I'd be so busy washing the darn towels.