If you aren't shooting them and testing to see which are going to fail, then leave them in the wrappers to sell in the next desperate scare that comes up.
They should be either proven users for the armory, or investment for future sale.
The real question is, how many do we really need? I've got mags, in the wrapper, and certainly not enough ammo to load them all if they were desperately needed. And I don't intend to sell them. So, something is wrong with my plan.
From that point of view, do you have enough using magazines for the ammo you have on hand for the worst case situation - or are they really just extra to take advantage of some future market?
It's not to say that extra mags aren't good - you can barter with them in certain circumstances.