It depends on whether your talking about fiber, b/w rc or color. Color is the most sensitive to change - unrefrigerated ra4 starts to show change in dmin and subtle shift in highlights in as little as 6-10 months. All kodak ra-4 paper has expiry dates printed right on the label. Fuji uses date codes.
Non developer incorporated b/w fiber and azo tend to age very well, showing little to no change after decades.