I'd say you would be just fine. Ammo sits out on shelves for months on end. Unless the environment is damp and the brass gets tarnished immensely, ammo can be stored for years. Powder canisters store their contents for years on end with no ill effects, and what you are doing is basically the same thing. The powder is stored inside the brass in an airtight situation. No need to worry about temperature swings, etc. Loaded ammunition is just fine in that regard. Your main concern is exterior brass or bullet deterioration from moisture.
My father brought home several boxes of 45ACP ammunition when he was in Korea. Circa 1954. I fired 10 rounds of it in my Colt a couple of years ago. It worked just fine.
The idea of putting a damp-rid or other similar product in with it is a good suggestion.
There's a fine line between BRAVE ... and STUPID.
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