I only added about 20 books yesterday, then let the indexing finish before charging it all the way to 100%. So mine went down a notch in about one hour w/o indexing being a factor. I do leave the WiFi on all the time though. Screen has mostly been at level 10 of 24. I'm having to use mine in short time spans due to the screen so it is difficult to keep up with the total time used since charged.