I have a can that I bought in October of 2003(I always write the date purchased on the cans). its been opened, and used, and the last time it was used was about 5 years ago when my son borrowed my T/C renegade percussion rifle for use during the early muzzle loader season. It went bang reliably, and I bet if I used it tomorrow it'd still function. If kept in a cool dry place where the temperatures don't vary too much, will last a very long time. .