Sounds good to me...
WiFi won't be on, when away from home. On the DS, I use the second lowest brightness, I doubt any higher will be needed on the 3DS either. Headphones, so the sound doesn't need to be all the way up. 3D will probably be always on, though but turning off the other stuff or keeping it low should help it last. About 5 or so hours seems resonable.
At home, it'll be always pluged in (like I do with my DS). Problem solved!







