Four Season Truck Campers with a Slide- really four season?

We camped in our Alaskan camper at Yellowstone when it was in the low 20s at night, with no wind.
No problems. It is pretty well insulated....as long as the wind doesn't blow too hard. The seals between the base and top is pretty good, but strong cold wind made a difference on a different trip.
It was/is probably time to replace the seals again. Easy, but time consuming. The seals need to be replaced about every 7 or so years for max performance.