10,000 recharges over the course of 20 years.Not bad. The batteries in Kindles probably have an undeserved bad reputation. The reason hardware makers use batts that can only be replaced in-factory is to increase the time between charges, thus the 17" MacBook Pro lasts a long time on a charge.
At least on the surface, that make absolutely no sense. The batteries used for a device and not the process required to replace them determines how long they last per charge. The process to replace them simply changes the convenience/cost.