RE: New to Li-po's
Um, that's not true. Cold actually PRESERVES the battery packs. They won't produce good power when cold, but they don't degrade as quickly. Thaw out the battery pack to room temperature by letting it acclimate naturally, and the battery will be fine.
If you put the pack in the freezer because it got hot, then pulled it out and discovered it was toast, it was the fact that you got it HOT that destroyed the pack, not freezing it.
You shouldn't be getting the pack that hot in the first place. If you're getting it that hot, you're using it too hard, drawing too many Amps. This is where a Whattmeter will help. At least you'll know how many Amps the setup is drawing. You can compare that to the specs to make sure you're not drawing too many Amps and damaging the system.
Replacing the ThunderPower packs with Electiflys? Make sure the Electriflys are rated to handle the Amps you're expecting to draw. If the capacities and C ratings are the same, you're okay. Smaller capacity and/or lower C rating? Be careful.