I only have 51 years behind me, our temps here never reach into the negative and rarely into even single digits, but sub freezing to well over 100 are the norm add 10 to 15 for the Garage in the summer time, where most people I know store they're powder, almost all the powder I've lost has been IMR powders, the one exception was AA 8600, that powder was a mis blended batch of AA8700, it was less than 2 dollars a pound back in the early 90's I believe, I bought 24 lbs of it, most of it went bad, I had perhaps 20 pounds of other AA powder only the 8600 was lost, and that was less than 10 years after I had purchased it, I took over the family reloading privileges about 71 or 72 to this day I still have several cans of misc powder left over from dad which predates my time behind the reloading bench by a good 10 to 15 years, powders like IMR 4198 4320 3031 Hod BC2 H335 H380 H450 H570 Alcan7 they all appear to be in excellent condition.