Longer than you would think, but if you're worried about it, dump it. I have some pyrodex that isn't that old and the pellets are stuck together......on the other side of that, i found some American Select in my grandpas shop(no climate control/farm shop) he died in 2012, found it a year or two later. my grandpa probably hasnt reloaded since the 80's. Opened it up, looked good, loaded some rounds, shoots great.
