I have a 2007 Jeanneau SO 36i, and I have the same system which you describe in the first paragraph. It is wired through a circuit breaker and I always make sure that it is on when I leave the boat. Fortunately I have very little if any fluid accumulating in that 8" cavity. It is usually dry. A couple of times, I have sponged out a small amount of fluid. I like to have it dry and if I ever see fluid in the bilge, I like to know where it is comming from.