No legal requirement,, but a good inspection and checkout at least yearly is a good idea. Our first trip out each year is to a local campground, and that is one of the things that we do, Go over everything, look for leaks, and things the rattle, Check all electrical, check water and sewer connections and conditions. I also schedule at least one trip to the shop for major oil and filter change, and mu mechanic does a complete checkout o everything while it is in his shop.