Originally Posted by chas0039
I am using 3 years as the maximum life of these batteries, based on technical web sites devoted to batteries. They seem to have a useful life regardless of the number of charge cycles. They start to die from the date of manufacture whether used or not.
A typical lithium ion battery will probably have lost about a quarter to a third of its capacity after three years. There are many people still using Sony PRS-500 Readers, which are now more than 4 years old, which still have an eminently usable battery life.