Fuji, does appear to have a shorter shelf life. I have some fuji flex stored in a cool basement that went bad after about 6 months. Oddly, the most significant aspect of it going south was that it could not achieve a good black. (this is unusual, most papers go south in the base or Dmin not the Dmax. My cleanout which is Fuji CA has printed pink in the Dmin for over a year, yet produces a real nice black when run through the processor.) I dumped and remixed all my chems to make sure it was the paper -- which was a waste.
Meanwhile, I have enduraflex which is every bit as old as the fuji stored similarly and is perfect.
I have a chest freezer which I have been too cheap to hook-up, but may have to this spring if I continue to use Fuji products.
FWIW I have no greater love for CA over any other paper. Except when printing specific films, I don't see any significant advantage of CA over Kodak. I use it because most people (those who might buy my work) have bought the hype and because it is cheaper. When I read or hear people write that CA is in a class of its own or that it is head and shoulders better than all others I think: Emperor + no clothes.