I have ammo cans full of primers and powder. Haven't had to buy
any since the big price jumps. I have powder sealed in unopened
cans that are at least 20 years old. All these are stored in GI ammo cans. I load hundreds of 38 WCs. My load 141gr cast WC
P5066 at 4gr. I drop charges in loading blocks of 50, randomly
check and before seating bullets use flashlight across tops to
look for possible over/under charge. I've had very few squibs
and the ones I did have were from punk primers. The flashlight
will let you spot problems with charge very easy. The storage of
primers and powder can be a major factor in producing squibs.
Best kept airtight at constant temperature. I'm still using powders that have been obsolete for years.