I did some measurements of the Cybook Gen 3 and calculated some energy consumptions. You can download the result from here:
Cybook_Gen_3_Energy_consumption.pdf
Shortly, one can do only about 3000 page flips for one fully loaded battery. Probably less. And the device is able to be switched on (without pressing any key or automatical switching off) less than 60 hours with firmware 708 or 40 hours with firmware 658.
I would appreciate any commnets (any error of mine is possible

). I would also appreciate any real world data - e.g. if someone counted real page flips (or computed from some book), or measured the time till battery runs out etc.