There are many documented problems with image longevity with RC papers. One of the first problems was the plastic coating delaminating from the paper base. The manufacturers have worked to correct that problem, but there are still problems with the images changing even when treated with Sistan or selenium toner. See Ctein's darkroom book on his problems with RC paper and subsequent tests to determine the causes. I don't know whether the manufacturers have solved the image stability problems documented by Ctein, although I'm sure they have worked on them.
I would suspect that you could better trust a fiber based paper to last longer than an RC print at this point as the paper formulations required for archival permanence are well known as are the processing requirements of the image itself. The RC papers have problems with the plastics breaking down from UV light - that's a tough one to cure with any type of clear plastic.
Personally, I would be equally suspect of the optical brightners that have been added as they too react to UV light. How long do they last, and what are the bye-products produced when they start to break down?
As for hardeners, I am not sure they add to the longevity of the print in any other way other than making the emulsion tougher and more abrasion resistant. Part of what the hardener does is cause the gelatin molecules to cross-link (polymerize) which strengthens the gelatin making it less susceptible to physical damage from handling, and swell less in the presence of humidity.