Sue & I have spent 5 nights in a row at 0 degrees F while x-country skiing in eastern Washington. No arctic-pack, 0 degree down bags, and no water in the tank. We run the heater only until the last one falls asleep. When we wake up, it is 0 degree F in the camper. I flick the heater switch from the bed and 5 minutes later it is 40 degrees; and 5 minutes after that, it is 60 degrees. The factory heater is really overkill for my 2007 Ranger. However, we have set up removable hooks by the door to dry wet ski gear and the powerful heater works wonderful for that. Sue makes me carry the port-a-potty in winter, so there is no going outside until the sun comes up. We get up, make coffee, wipe the condensation of the inside with micro-cloths, pop down and head into town for breakfast. I have an arctic-pack but have never used it. We have friends who have a conventional cab-over camper and they have the exact same problems except there heater does not cycle as often, due to more insulation. There is no magic bullet.