My experience with Agfa MCC is that it significantly fogs as it ages, more so than any of the other main paper manufacturers. Several years ago Agfa UK sponsored me to do workshops using MCC, a paper that I loved at that time. They gave me 3000 sheets in packs of 25 to take with me when I did workshops, in less than two years it had lost contrast and fogged to a mid grey after about 1 minute in the developer.
I recently got a new batch of Ilford Warmtone from Ilfford UK and compared it to the last of the same paper that I had in my darkroom and that was just over two years old, it was at least 1.5 grades lower in contrast and the paper base fogged slightly as I developed it. I would certainly not recommend keeping paper for more than two years. Having said that, I still have a supply of the old Agfa Record Rapid and Broivra that is at least 15 years ols and occasionaly make a print on them. The white paper base fogs and the contrast is greatly reduced but with a little chemical help I can get what I want from it. In my experience the Agfa Record Rapid from pre 1985 is still the best paper that I have ever used, followed by Kodak Ektalure now gone, but I still have a supply of 16 x 20 in the freezer.