Most phones use a type of Lithium battery, and are nearly fully discharged daily and charged overnight. They still last 3+ years before battery life becomes a large problem. An ereader that will be charged every few weeks to few months at most will last a whole lot longer than that, even when doing full charge cycles. And IMO, total battery capacity is something I'm a lot less worried about with an ereader than a phone. Charging the device every 2 weeks rather than every 3 is not something that particularly bothers me.
Thank you for the advice Compurandom. But I'd rather take a smaller capacity battery that reads correctly over a larger capacity battery that I never know what the actual charge is!