Tom/Barb - Newells are not fiberglass they are aluminum. But your comment is valid, time takes a toll on everything.
OP - your thought process is valid about buying an older high end RV versus a newer mid range. I have been exeposed to many Newells, Marathon's, Liberty, Millenium's and their owners over the last 3 years here at Motor Coach Country Club in Indio CA. One thing that many state is that they prefer a coach built on a bus chasis (Prevost) instead of the custom chasis (Newell). They have stated that the ride is better and there are less issues when using the bus chasis.
I love the Newells myself, went and did a factory tour and love the layouts and designs, maybe soon I will have one.
Do your research before you buy.