Dean,

If you want an extra layer of safety, you can store your big packs in LiPo sacks. You can get a couple of 10S packs in each bag, so the downside is you would need several bags to hold all of your batteries. That being said, I have not had any issues with storing big packs either sitting by themselves on shelves or in cases like a transmitter case or one from Harbor Freight as you mentioned.

Take care!