[jhautz]

Ive got over 3 year old TrueRc 2s and 3s 8000mha packs Ive been running in series for a 5s setup in my revo. 3 years and still kicking. I charge them and balance them in series too though so they in all reality have been treated the same as a single 5s pack. As long as both packs are the same cells and always run together there should be any issues at all. Its very common practice to do this.