I'm not sure what you are asking.
If it's whether auto-lock saves battery, then probably yes. If you forget to turn off the iPad's screen manually, then auto-lock will turn it off for you after the set time. The screen is the biggest drain on battery life, so leaving it on when you are not using the iPad will have a huge impact on battery life.
A short time for auto-lock is best for battery life, but can quickly get annoying if you are reading or doing other things on the iPad that don't require you to touch the screen a lot. I keep my iPhone at 2 minutes and the iPad at 5 minutes, and rarely run into the screen shutting off.
Video playback disables auto-lock until the video is over; so you don't have to worry about the screen shutting off while watching movies.