[zeropointbug]

There really isn't an "end" for batteries, you decide when this end is... from the time you buy lipo's and start using them, their internal resistance goes up, and mah capacity retention goes down, after every cycle, bit by bit. Standard ratings go by the 'end of life' at the point where only 80% of it's original capacity is left. But, as well, the internal resistance goes up too, and performance is a product of resistance (chemical resistance) x mah capacity, so performance will go down exponentially, unless I am mistaken.

A123's are a littel different in cycle life aging, they are the first battery chemistry to actually have their internal resistance go DOWN over time, but of course their capacity goes down as well... so if you look at cycle life charts of them, their performance stays the same over their entire life! Only mah capacity is reduced. Although, they don't perform like high end lipo's, and they only have one cell size, I love them, and have been an early adopter from the start.