[How to you store yours for long term keeping?]
Around my waistline...
Seriously though, I would think that an airtight container - say 200 or so .50 cal. ammo cans - stored in a cool place would keep chocolate fresh for a long time. If it got a little stale, so what? If SHTF time comes, I’d eat it stale or not.
Look for Nestle Quick at Mexican food markets. It comes in CANS not foil lined cardboard tubes. I purchase a number of 14 oz. cans for $2.00 each on sale.
Also I recommend Augason Brownie mix just add water and bake! Great chocolate fix!
http://www.augasonfarms.com/Bakery/Chocolate-Fudge-Brownie-Mix-10-Can-UPC-00946-40024
Chocolate does not go bad, though if it gets too moist it can “bloom” with a white coating, which is not mold, and you can still eat it.