I'd ecstatic if my O2 would only use 37% in 4 days.
You guys need to stop thinking in days or weeks. It means nothing if you don't also look at the time the device is actually used for reading. And then there are other variables while doing the reading.
Gimme 10 days of battery any day. None of my kindles have ever been able to go 10 days.
At this point I'd just rather be reading books than obsessing over my battery life. I turned off the accessibility setting that gave me percentage. I am not looking at it anymore. I know I have to charge every 2 days. Or after I read 2 books. Long ones that is.
. I like to charge before I get to 33% down.