I've got duals on a Fleetwood 37'. One ducted/controlled by thermostat and the second is non ducted. My problem is the none ducted blows right down onto the thermostat which sometimes shuts off the ducted one. I have never left either of them on when I'm gone, nor do I know anyone in my park that does. I would be afraid of burning out the compressor and having a huge $$$ bill each month.