Only recently tried a "dry" camp trip, and was reluctant to run the furnace through the night. However being Alberta and "spring" (also known sometimes as 2nd winter) with 2 young kids, I needed to have the heat on. I also do not have a generator.
It worked just fine. With a few minor details. The first being I had left the furnace off until I went to bed which was well after midnight, then I turned it on. We had a solar kit installed when we bought the unit, so even late into the evening (sun doesn't set until well after 10pm around here this time of year, and is rising by 5:30am most mornings) the batteries are pulling a charge. I have also replaced all the light bulbs in the unit with LEDs, but even still we only had one light on when we were inside which wasn't often after the kids were in bed. My wife also boiled a kettle of water on the stove for a cup of tea, and heated some water in a pot for doing the dishes after dinner, which threw enough heat into the camper, that even after I turned the furnace on, it didn't come on for roughly an hour.
I keep the furnace at 60f and it is sufficiently warm for both us and the kids, but not so warm to require a whole night of running. This was pretty much the same thing for both nights we were out, and they were mostly sunny cloud free days. Overnight temps dropped into single digits celcius, but up near 20c during the days. Perfect camping weather in my opinion.