Good Evening,
When I started doing darkroom work in the '70's, I began using Kodabrome RC as my contact sheet paper, and I continue to use it. A couple of years ago, I spotted on E-Bay a 250-sheet box of 8 1/2 x 11 and won the auction. I suspect that the paper is at least eight to ten years old, but it works fine for contact sheet purposes; I have a lot of it left and will continue to use it. Gradually, I'm noticing that the whites are no longer as clean as they should be, but I think it will be OK until the box is empty (another year or two, probably).
Konical