If I'm at home where there are four guys (two of whom are the complete opposite of clean) sharing the same bathroom, then I try to do it once a week.
Here at my dorm at university where I'm (normally) only sharing a bathroom with one guy who is reasonably clean, I do it about once every 2-3 weeks. The bathroom being shared between my other two roommates, though...oh, man, words do not describe the filth of that bathroom. I mean, I've seen worse, including from my family when I return home after months of being away, but that it is still absolutely horrible. But I almost never use it, so I just don't bother trying to clean it. I'll leave it for the cleaning crew that comes by once a semester (which, coincidentally, is this week).
Here at my dorm at university where I'm (normally) only sharing a bathroom with one guy who is reasonably clean, I do it about once every 2-3 weeks. The bathroom being shared between my other two roommates, though...oh, man, words do not describe the filth of that bathroom. I mean, I've seen worse, including from my family when I return home after months of being away, but that it is still absolutely horrible. But I almost never use it, so I just don't bother trying to clean it. I'll leave it for the cleaning crew that comes by once a semester (which, coincidentally, is this week).