The day I get 10 days out of a kindle is the day I know I am not reading enough.
I think I read like 2.5 books over the holiday on one charge. I charged at 40% though so I guess I could have read more than 3 books if I had let it get lower. But it happened to be night time then. These were fairly long books with 400 some pages. I got not quite 2 full days on that. And it was a constant start and stop, open close cover, flip screen over and all that. I was reading in between cooking and other chores.
Even on my Voyage and old Oasis1 I had to charge like every 3-4 days.
I think its pretty clear overall that the O2 doesn't last as long as the O1 or Voyage. But it is what it is.
Heck, I just pulled my keyboard from the shelf. I charge those up once a month, all my old kindles. The keyboard had full battery still. Totally full. Sat there for 2 weeks or so. I can't recall when I charged it last, been a while though.
Since I can charge the O2 while I eat, or while I fold clothes or such thing, I don't worry about it. I just love the thing.
I am actually doing a experiment and leaving wifi on. I want to see how much time I get. I'll probably go back to non wifi, but I do like being able to go to wiki and other things whenever I want. I do look up a lot of stuff.