We have an International with panoramic windows on both sides -- Aluminum walls, too! We lived in ours from April 2008 until now with occasional trips home to our condo. It's been in zero temps and 100s.
One trick we do to keep cold leaking into out unit from under the bed storage area is to block the side "holes" with a sheet of styrofoam.
We used our furnace with a small ceramic heater and it stayed toasty warm. Better yet, some snuggling
under an electric blanket made it real comfy-cozy.
The AC works great. We upgraded our AC unit, but now we hear they put a bigger unit in our model.
That's why purchased an airstream. For year round use. LOVE IT!