Funny,

Even the smallest servo and RX combo will never last 12-13 flights reliably with a 600-700 MAH pack. That is, unless the flights are very short and unventful.

Long ago, I switched to LiPoly. Larger capacity, less weight and more reliability. I really like the stability and shelf-life too. NiCD and NiMH are fine, just heavy, bulky and a bit too 'old-school' for me.

HOWEVER, they are cheap, fairly reliable, and the weight savings of lithium is really only important for aerobatics and pattern.