I was trying different "pet" loads in a new GP100 when I came across some .38 Special "accuracy" loads I'd put together in 1976.
That ammo along with a couple of boxes of .38 GI Ball ammo has been in car trunks, sheds, etc. etc. from Southern Nevada to South Carolina.
Both still shoot as well as new --- as have a brick of small pistol primers that I had marked "1989" when I bought it, and every one of them worked perfectly this past fall and winter.
I am not suggesting storing your ammo and components in extreme conditions, I am just saying that I have never had a problem.
JMHO - YRMV