For a while I was washing/detailing mine about once every 4 weeks, but I've been bad this cycle and by the time I wash it Saturday it'll have been dirty about 5 or 6 weeks.
It's hard because I don't have a space at my apartment to wash it and the self-service wash places I've seen don't let you bucket wash if it's crowded, so I usually go to a relative's house on a weekend. But weekends have been busy lately.