I'm sure others will jump in with more technical/accurate information but here is my take. The 8000 page turns is actually 8000 screen refreshes, so every time you look at a menu or start up the Cybook or flip between pages of eBooks in your library you are using up some of your "page turns." I have never counted the number of refreshes I get, but I do know that I get at least a week of reading time out of a single charge.
I read at least 2 hrs a day every day, on the weekends or holidays this could go up to 4 or 5 hrs a day. I recently went on holiday for a week, I had a fully charged Cybook when I left, read 3 eBooks and part of a 4th, and still had some charge left when I got home. This meets my needs in an eBook reader.