The only problem I could see is that sometimes battlepacks will have small holes in the pvc due to the process of shipping and/or handling. I had this problem on some SA where the packs were shippped in a cardboard box. When the box was delivered to my door, it looked like someone had taken a bat to it. Anyway, some of the packs had been compromised as a result of UPS beating the sh*t out of my package.
As far as SA battlepacks go, if you are worried about moisture, 7 of them will fit perfectly into a ammo can for linked 40mm grenades (and I mean perfectly, you would swear the can was designed for this purpose). The can looks like a smaller version of the big 20mm ammo cans, with two latches and diagonal ribs on the side of the can for reinforcement. The cans are hard to find though, wish I had bought more of them when I had the chance.