Issues with older models?

I'm in market to buy a pre-owned TrailManor. On most of the classified RV websites, there are many models from '99 to '02, but extremely few older models from '94 to '98 -- does anybody have any opinion as to why that is?

For example, one dealer told me that '94 models had wood versus aluminum "inside-framing" and that they were more likely to rot (any truth to that statement)?

Thanks for your insights.

Robert in SoCal