I ran my IB4200WC for about 9 months ... and started with 6 packs of 6cell. Performance is good - punchy. From time to time, I have problem on individual cell and I will remove the cell from the pack and part the rest of the cells as spare for future use.
Most of the cells died recently - I think it is fair after being used for 9 months. A few of them dired (leak, smoke ... etc) died during charge cyclone, but most of them were dead during running on car (5 min run with 3.5R) and it expanded and became super hot ...
After 9 months, I am now down to 2 packs of 5cells only ...