1st, the Hitchhiker has an excellent reputation. The last problem I would expect is any frame problems.
2. Our Lifestyle does not have dual pane windows either. It certainly hasn't been a problem in the summer with dual AC. I don't know about winter in the ice belt. Generically I've read problems with condensation between the panes. Unless you are full timing in the North I wouldn't worry about it.
'14 RAM Longhorn,DRW,4x4,CC, LB, 4.10, Aisin, 70gal underbed fuel tank.
Lifestyle 36FW, 8000lb axles, disk brakes, 19,100lbs
Andersen AL Ultimate hitch