There is another thread going on right now about this same thing and it has been garnering both the every year advocates and the every few years group as well. I think it depends on how much you use it and how well you clean it. You are protecting your investment with the professional cleanings and check-ups, so I don't really think there is a hard and fast answer. I have mine cleaned every few years just because I have to drive so far to find an authorized technician.