Archived - How to listen to video podcasts and conserve power
On an iPhone, iPod touch, iPod classic, and iPod nano (3rd generation) you can play back video podcasts with the display off to conserve battery life while continuing to listen to the audio of the video podcast.
To do this:
with iPod touch: Choose Music > More > Podcasts.
with iPhone: Choose iPod > More > Podcasts.
with iPod classic and iPod nano (3rd generation): Choose Podcasts.
To play back both video and audio, start the podcast playing from the Videos menu.
For more information on battery life, click here.