I too have 30 year old RC prints that are still in good condition, no fading, stains or cracking. Ctein has made some silly claims about RC materials in one of his many rantings but my experience does not agree with his so called scientific findings. I'm with Lee on my feelings about the look of RC paper, the image appears to sit on the surface, that is the only reason that I don't use it.
My experience with colour negative is the same as others, serious fading and colour change after 20 to 30 years.
Digital is in its infancy and we just have to live with what we've got but I'm certain that the manufacturers will crack it given time.
To answer your question Frank, Properly processed black and white, RC or fibre, will be good for many years 75 to 100 years perhaps. Colour negative is dodgy and digital is in the hands of the scientists.