The RoadTrek lifetime warranty would certainly be interesting to investigate since five years ago when I checked into them, they roughly cost about $1,000/year.
From what I've read on the forums, I'd steer clear of Class Bs based on the Promaster as besides being front wheel drive, they are displaying signs of unreliability and underpowered.
About the only way they could get R-32 factor insulation would be by using Yeti vacuum tech.
Glass half full or half empty to an engineer is the glass is twice as big as it needs to be.
PM me for sale info on my 2011. SOLD!