Different camper here- but I keep it on if I want to have any hope of seeing any reflections in the mirror when I'm done my HOT shower. I leave it on a while afterwards hoping that the moving air dries out the room quicker (not sure how much wishful thinking this is, though).
That said, there was a recent Sabre thread where one posted said his air conditioner units dripped condensation more when the vent was open and fan on. We left our fan on for the better part of last week and definitely did notice more and dripping condensation. I didn't put two and two together at the time. My next trip, I'm going to leave it off unless someone is actually showering.