After living with the disabled screensaver on the kindle 3 around home for a while I have found the battery life disappointing. I used it for an hour per day and hard shut it down between uses. I didn't keep track but it didn't take all that long before it started warning about plugging it in. I am pretty sure it does better in the normal mode battery wise. Not sure why.

I think I'll try not turning it off between uses just to see how much better or worse it is before giving up and turning the screen saver back on.