Storage has a lot to do with it, and I've seen variations in prints produced around the same time on the same paper.

The RC papers of today are quite different from the papers of the 1980s, so they may last longer than those earlier papers, but this is as much "in the hands of the scientists," I think, as what to expect from digital output materials.

Fiber we know is good. Kodachrome seems to have held up well. I have Cibachromes that are at least 15 years old that show no fading or shift.