I just happen to be testing that again presently: I'm down to 2 bars, and I've not charged it for a couple of weeks, which is about what I anticipated, and about what I got the first time I tried it in October.
In any case, if it lets me read all day and charges up overnight when I'm sleeping, I'm pretty cool with that as a minimum. Of course, it's still giving me a great deal better than my personal minimum.
