Li-ion batteries have a fairly high self discharge rate (compared to common Alkaline cells). A fully charged battery sitting disconnected will lose 15% or more just sitting there, per week.
I learned the hard way to charge the Li-ion batteries (and spares) for my Digital Camera the night before use.
So, while the battery might be actually good for 8000 page flips, normal speed reading
probably will not see any where near that number due to self discharge and other use factors.