We camp more in the winter than summer and routinely stay out with temperatures down to single digits. As long as we have electric we will camp and have done so for past 7 years without any issues. With the furnace or electric heater on, foam spray, thermal windows and extra insulation has kept us warm inside. We winterize the trailer unless water is available and we carry a heated water hose.
What you get by achieving your goals is not as important as what you become by achieving your goals....