freeair, you are correct, it is possible for a battery to fail in such a manner that it won't make any difference HOW many cells you have. In my 30+ years of RC flying, the vast majority of failed NiCd cells I have ever had were shorted cells, not open. They still pass current, you typically just lose the 1.2 volts from that particular cell. That's not to say that open cells don't happen, it's just been my experience that the shorted cell is much more common.
There is no perfect battery. I'm old fashioned enough to prefer NiCd cells yet, I've had not so good luck with NiMh cells, and don't want to get into LiPo's and the required chargers, etc. I'm sure they work well for the folks that want to use them, I"m just not there yet. Heck, I just got a 2.4 GHz radio, haven't even put it in a plane yet!
