Although Brendan's tips are good, there's evidence that some Wi Fi access point connections drain the N800 unreasonably quickly. If you search around for people complaining about their N800 dying overnight, this is what you'll find. I personally see this -- I have two APs in my home: one kills the N800 overnight, the other can be connected to in standby for days. As far as I know, there's not solution to this yet, but if you have an old AP lying around, you might try setting it up and seeing if the improves things.