My recommendation would be to separate your audio/video player and mobile phone/wi-fi device. Apple products just don't have the battery life for a all in one device (like the iPhone, iPad, iPod touch) IF you are going to be using the audio/video sections for extensive periods of time like 13 hour plane rides. I would recommend something from Cowon like the s9 or d2 (or whatever) that offer extensive battery life like 50-60 hours for music 10-20 for video. Get a phone of your choice and you are set for the even the most demanding portable audio/video use (and by your original post that seems to be the case)
Both the battery life and media format support (MKV OGG) of the Cowons looks intriguing though at some point I might have to resign myself to using one standard format for simplicities sake. Something akin to your recommendation of separating some functions seem to be that way to go as no one thing seems to get it all right.
