Pretty sure I have some ammo from the 40's or 50's in steel tins inside of wooden crates 7.62 x 54 and the one tin I opened and shot from was fine. I do think you should buy bulk and store with the intent of passing it down to the next generation. Although my kids like to shoot so I think they would always appreciate it.
Another thought
I personally have ammo I bought in the 90's off retail shelf with price tag still on the boxes, I wish I had bought more as it would be a steal in todays pricing.........