I have boxes of paper 2 years old or so at room temperature. They are fine. I also have few more boxes that I don't plan to use for a while in sealed bags in refrigerator.
According to Simon (who runs Ilford), its paper products are good for at least few years - longer if kept refrigerated. He said something about not putting expiration dates because retailers went nuts when done.
My understanding is, their life span is in years not months. I seem to recall a figure, 5 years, being tossed around as a safe expectation.
My suggestion to you is only buy what you expect to use in a year time - and not more. This is because your taste in paper will change, not because they go bad.