I quit riding at some point every year. At some point, the urge to get my hiking boots out takes over, and if that doesn't happen, eventually winter sets in and I go skiing again.
My three-activity year helps keep everything "fresh". There's always one activity that I haven't done for a while, so if it's getting to the point where I feel like "oh. riding again" I can just lace up the hiking boots and go do that. Or vice versa.