That sounds like your getting some really good speeds out of hardware that is now technically obsolete, I'm quite jealous. I do not blame you at all for mining for heat, last winter I had 2TH of sha256 asic's mining bitcoin just to raise the temperature in my cold house, it was very effective and the bitcoins I mined were also very helpful.
As for my battery packs, I was concerned by thermal runaway at first that's the reason I fused at 3 amp rather than 5 like most go for, but I've had the set up running for at least 3 months now, I'm yet to have a cell even start to get warm, trust me I'm testing regularly feeling for any heat. The day a cell shows me any kind of heat is the day the battery bank gets migrated to the shed, hopefully this day will never come though as the shed is a lot colder and may affect the chemistry of the cells. There is always something else to consider isn't there. :)
Sorry but I regret selling some of my other miners, id rather keep hold of what I kept a hold of now, just in case something happens and I can use them again.