IMO, it would depend upon where, and how, the firearm(s) are to be stored.
If I were storing any that were to be undisturbed (buried, etc), after the mandatory thorough cleaning & lubing inside/out, I would pack it with a gun perservative grease, stuff it in a blue bag, and glue it into a piece of PVC with a glued cap on each end while it was in a dry-humidity enviroment.
Barring that, I would mimic military long storage - suspended in a sealed , re-inforced wooden crate I built to fit, on internal brackets, after the same pre-storage maintainence.
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