We camp in temperatures down to 10 degrees although try to find places in the 30's over the winter. We never stored ours for any season and used it year round (rain, shine or snow). Ours had two large single-pane picture windows and a slide out jack-knife couch section on the other side which was not insulated well either.
The plus side was ours was the shortest wide-body model. This meant the frame was very robust for the size, it had 50A service, 5.5kw genset, 40 gallon fuel plus dispenser, dual 75 gallon fresh, 10 gallon hot water, filtered water dispenser and more. It really spoiled us compared with the fiberglass egg or popup tent trailers we had prior. We are on second truck camper now, but that is discussion for another section of this forum.