No problem leaving them for years, if the primers are not subjected to moisture or intense heat. I often have primed cases sit for long periods of time with no degredation.
I have also had primers submersed for days in water that worked fine after a long drying period. That was twenty years ago or more, and the few remaining of that batch still work fine.
I am using World War II surplus 4831 that still gives the exact same balistics as it did when I bought it 30 years ago. Also 20-30 year old powders of a number of types -- flake, ball and extruded, single and double base, that have accumulated over the years. I have never seen a problem with any of them.
For practical purposes, these components last a lifetime if you take some care with their storage, and often even if you don't.
Posts: 283 | Location: Florida | Registered: 12 August 2001