Construction of older models

[vic1000]

I've been reading and learning. We're thinking of buying a TM. I read one post about a 1990 model 28 and they were talking about rotting wood in the walls. I was wondering if anyone knows if Trailmanor used to use wood to frame the trailer differently than they do now with the aluminum frame and polystyrene. If so, what year did they start making them like the new models they are making now. We were trying to find a good used 2720SL , but I want the current construction methods and I don't want something that will rot.
I appreciate any information.
Thanks,