Dave R said:
I don't currently have any cartridges to use H110 on. Dang, I may have to buy a .44 or .357mag, or an M1 carbine, just so I have a way of using up this powder.
Now your talking like a shooter. The only missing part is where you have to explain to your wife why you "need" a $600 gun to avoid wasting $25 worth of old powder? I would try something like exponential value growth of the investment in the original by what it
could have earned in an S&P 500 index fund over the same period, and equate that to its current value. Avoid answering questions about the relevance of the comparison.
Ruger4570 is right that "ideal" conditions for stored powder are “flexible” based on how long you intend to keep it? The ball powders, like H110, have a little acid neutralizer in them that scavenges acid byproducts of deterioration up to the point it is consumed. The powder might grow a little weaker, but wouldn't fail until that was gone or it got wet.
Modern non-corrosive primers are the most sensitive thing to storage deterioration. According to a post on Fr. Frog's site, as little as one summer stored in the trunk of a car can make them unreliable. In the southwest, I know it can get as hot as 170 degrees in storage containers left in direct sun. I doubt the trunk of a dark colored car could be far behind if it isn't shaded or moving. But powder will still survive that treatment. I just don't know for how long?
I also know the development of the ball powder process was important in WWII because it allowed nitrocellulose in deteriorating old artillery powder stores to be recycled into rifle powder. Something went wrong with that artillery powder, but I don’t know what or how well it was made in the first place? I've also read that Alliant still has samples of original lots of Hercules Unique and Bullseye (introduced in 1913) that it tests from time to time and that they are still good. Maybe I should try to find out what their storage conditions are? I don’t intend to live another 100 years, though, so I don’t know how useful that information would be?