Our 2010 Bounder kept us through two very cold, blustery nights last February, minus 4º and minus 6ºF, at an Elephant Butte, NM RV park. Obviously we had the propane furnaces running all the time (went through nearly half a tank), along with a small electric heater. The rig had been winterized, but the fresh water and holding tanks are heated, in any case (not all the water lines, though). Showers were taken in the RV park's building (nice place).
We did close the slide on the second night, because of the noise from the slide topper in the strong winds, not because of being too cold (though it did give us less space to heat).