[cannonboy63]

I think it's important to avoid really bad conditions. At the same time, let's not make perfect the enemy of good. The important thing is to have the ammo. Store it the best you can. While I agree 70 degrees with low humidity is great, it's not always an option.
Having a climate controlled, humidity free storage area is unlikely unless you have more money that you can deal with.
Ammo cans were truly designed well. They are sealed, easy to transport, stackable, and available at reasonable prices. A little dessicant in each can and it's all good, IMHO.

 

[cannonboy63]

Also, I have a number of military ammo cans, military surplus, of course. The outsides are sometimes rusty which steel wool and WD40 takes care of. But ALL of the insides are rust free, if the can was kept closed apparently. So I think these are the ideal solution. If you want to store them under your bed in the climate controlled house, that is perfect IMHO, and makes use of space seldom used. As a bonus you can't do vaccuming there anymore.
I do like the plastic cans from Harbor Freight, too, but I am not sure they seal like the Army cans. They would work well under the bed tho.