The quality of your WLAN access point heavily influences the N810 battery drain. For example, I noticed that my new Zyxel ADSL+WLAN box caused the N810 to drain its battery in a matter of hours. The tablet was warm to touch the whole time. On the other hand, an old WRT54GS v1.1 allows the N810 to remain in standby for days, even with IM presence set to "online" for most of the time.