Tonight I tested how much battery the Nook will use with airplanemode

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So it used within 12 hours only 4%.
So that would mean: wifi: on, airplane mode: on put to sleep it would last for ca. 18-20 days if you don't use it
Wifi: on, airplane mode: off, put to sleep it would last ca. 10-12 days
Mine uses ca. 5%per hour, when I'm just reading. When the touchscreen is of and I just flip pages. So I could read ca. 16 hours without charging it new. That is absolutly ok for me.