I have used BT reloads from 1995 with no issues. I think they will last a long time. For some reason a hobby shop I visited a lot got around 50 packs of F39s around 1995, I think they thought they would be huge sellers. Folks from our club would buy a few packs here and there for the next 20 years. When they closed shop 20 years later they still had 15 packs which I got at a good discount. They burn great, good thing I love that motor.