[It strikes me that the latest level RC from Ilford for instance has maybe only just turned 20 years old and maybe not even yet?
I have first generation Kodak and GAF RC prints, the Kodak prints are holding up. I think paper manufactures were (perhaps still are) concerned about claims that would not hold up in the field, leading to overall distrust of the new paper. Few users needed a commerical print to last for more just a couple of years anyway. Aside from testing in the lab no one really knew what the life span of RC was going to be so I think Kodak and other errord on the side caution. I dont see why a RC print will not last 75 to 100 years, at least in storage.
All very fine and good if you're truly looking for a commercial print for an admittedly temporary purpose, but what good is a photographic image if it only lasts beyond the lifetime of the original photographer and/or the original subject when kept in dark storage?