I'd say the newer guns will last a couple generations and longer. Plastic has come a ways, but for a real heirloom rifle I wouldn't want a rifle with any significant parts made from it. Some of the heat treating is better and some springs on the new stuff are better than the very old rifles.
Wood stock is the way to go, I think, and well polished steel is harder to scratch and rust.
I wouldn't buy just about any manufacturers "budget" gun. Too many cost cutting measures, and often substandard designs and materials.
The older stuff might better crafted in some ways. No MIM or cast, and generally I prefer a *real* control round feed, with a real Mauser 98, or a commercial clone.
What I'd look for in an older rifle, would probably be an older Brno, older Tikka when they were their own company and still made from all steel. 60's Husqvarna before they went to a push feed, probably about a late 70's-early 90's (thereabouts) Remington 700. Newer probably a Winchester 70 and probably a Super Grade for the fixed claw extractor. Sako. Weatherby, but a real high grade, and not the Vanguard, though the old ones were pretty nice. The newer Weatherby are Howa, which could be the best budget rifle made right now. I believe the old Smith and Wesson as well as another couple rifles I can't recall were also Howa, but higher grade, with nice wood and a better level of polish.
