I now have an unopened package of FX520, Panatomic-X sheet film in 2.25 x 3.25in format, 12 sheets. "This film must be developed before Jan 1941" it says on the box. I have used 30 year old Tri-X and 50 or more year old VP, so, extrapolating, 80 year old FX should be just fine. With a date of Jan 1941, I am not actually sure when it was made. I should save some until Jan 2021, and maybe Jan 2031 and 2041.