Also, electric blankets are nice to have on the bunk ends. We got hit with unexpected cold and even with our heater in the popup, the bunkends were chilly. We bought some nice heavy blankets at the Mexican pavillion one night on the way home for about $18 each and they were perfect.
A tip on the heater.... Get one that oscillates (moves from side to side) that way the entire camper gets heated and not just one area. You also want one with the tip over and overheat protection. You also want it to have a high blower speed to get it to the bunkends. We put ours on the stove with the stove cover closed. That put it in about the center of the camper and not near or on anything fabric or wood. Other than on nights below freezing or with lots of wind, it kept us toasty w/o needing a heavy blanket.
Temps below freezing are not common and if it is expected to get that low, a freeze warning notice will be posted at the Comfort Station.
Happy Camping!!