All color papers are quite prone to staining if the blix action is not uniform and rapid. Both Fuji and Eastman Kodak recommend the use of a stop bath to prevent this type of problem.

I have kept Supra III on the shelf unrefrigerated for a year or more and found only a slight change in red speed (prints become red as the paper ages). So far, with limited data, I find that Endura seems to keep better. I have no data on CA.