If the backlight on your device is not on long enough (or is on too long) for your liking, you can easily change the duration for easier usability or longer battery life.
1. Go to the Home Screen on your Device.
2. Press the menu key to show all your applications.
3. Select Options.
4. Scroll down the list and select Screen/Keyboard.
5. Select the Backlight Timeout option and choose the desired duration (10 Sec, 20 Sec, 30 Sec, 45 Sec, 1 Min, 90 Sec, or 2 Min).
6. Press the menu key and select Save.