To save power, your Kindle will go into sleep mode after a specified period of time. Depending on what you’re using your Kindle for, you might want to change this setting. To do so, go to your Settings then the Display & Sounds menu. You can change the Display Sleep timer to whatever you want.
I usually have this set to 15 minutes. If I’m using my Kindle to listen to music or watch a movie, I change this setting to Never then change it back when I’m done. This is also handy for those times when I need to download a large file, sync a lot of content, or for applications that take a long time to update.
When using this option, it’s important to either change your timer when you no longer need it or place your Kindle in stand by mode otherwise the device will stay on and drain the battery.