Officially, the unopened shelf life is 5 to 7 years per the Coleman site. The opened shelf life is 1 to 2 years.
Quote:
An un-opened container of Coleman® Fuel stored in a dry area with no rapid extreme changes in temperature will remain viable for five to seven years. An opened container stored in the same area will remain viable for up to two years though will be at its best if used within a year. Coleman® Propane Cylinders can be stored indefinitely in a dry area. The propane fuel inside the cylinder will not break down.


However, I've used 30 year old Coleman fuel that was in my uncle's old Primus 71 stove without any problems whatsoever. YMMV.

HJ
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Adventures In Stoving