Hi,
The powdered chemicals from both Kodak and Ilford that are in sealed pouches from the factory generally have an indefinite shelf life provided they are maintained in a reasonable storage situation. This is informally from both Ilford and Kodak techs. Last week I mixed a batch of Kodak's XTOL which I had on hand since 1998, and it was fine. I still have in stock one batch of
Ilford's IDII Plus which I have been saving since the late '80's for a special occasion. (The current ID II dropped the "Plus", which was Ciba's B4Z, an anti chealating agent in Cibachrome, back in the late '80's).
Note: One should always run a test roll on something like this before running something
important.