Airstream models that I've seen do not have the thermal package that Arctic Fox has nor do they have the 4 season capabilities that the Arctic Fox has.
No argument nor am I trying to derail your Arctic Fox trailer acquisition. However, you did say you wanted to keep the next trailer for a VERY long time and the statistics are on the side of Airstream for building something that lasts, has no filon sides, no rubber roof, etc.
That is not taking anything away from any Northwood Product if that is what you really want. You might check into what the Four Seasons
package is and into R factors for roof, walls, and floor for insulation. In my assessment the real advantage of the Northwood products are the frame. The axles and all appliances are off the shelf for any manufacturer. Filon is filon, rubber roof is rubber roof. However, very few trailer manufacturers make their own frame. And it is stout.
Since you have a Ram/Cummins you can easily pull more than a 22G trailer. You might look into the larger sizes as they are roomier, spacious with the slides (not all slides are letting cold air in as Arcitc Fox's have double or triple the slide rubber seals) and your concerns about slide issues on their trailers have been minimal.