Battery Life of ipod when watching movies???

Hi there guys, just bought the new ipod video, I have had it for 2 days now, last night i put a movie on my ipod 5G video, and watched it on the way to work, am a bit concerned as my battery has only lasted (from full charge) the duration of the movie, do i have a faulty battery??? what's your battery life when watching video???
what good is having 30 movies on your ipod, but only have 1.5 hour battery life??? anyone else have this problem???