At night we turn our furnace down to the lowest setting. That is 52 degrees with an old school honeywell thermostat (non-digital). If you are camping with electric hookups, turn on a couple of electric heaters. Our 17' camper only needed one heater and it stayed nice and warm. Our furnace never turned on.
Last month we dry camped for 9 days with highs in the 50's and lows around 15 degrees. We just installed new golf cart batteries and did not have any problems running our of battery juice. We just ran the generator for a couple of hours in the morning to top off the batteries. Great camping week.