If you ride it all the time, every month. With 20-50 in the summer if its hot in your area and 10-40 in the winter.
If you dont ride that much every couple months is fine.
I'm in my late 20s, and it's really hard to find jeans around here. I went to the mall, which I haven't done in years because I'm going back to school after a year of having been laid off and don't have anything that doesn't have grass stains all over it from yard work. Everything is either...