While there are plenty of apps to choose from to manage killing running applications, I am going to focus on one of the most convenient and simple to use for the casual Kindle Fire HDX user and this is Advanced Task Killer Free. This app simply shows you all running applications that aren’t critical OS related processes and simply lets you check mark and kill the processes, but more than that it allows you to configure auto-killing applications when the screen locks as well! Ironically the app can select and kill it’s own process instantly closing it when you click KILL selected apps as well.
Click on your triple dot settings icon, and go into app settings and you can go into Auto Kill Level and set how aggressive you want Advanced Task Killer to be when it comes to killing apps. I chose safe to start with, though found no real difference between Safe and Aggressive.
Then afterward you simply set your Auto Kill Frequency
You can have it purge apps every hour, 2 hours, 4 hours, 1/2 hour or only when the screen is turned off. If you tend to set down your Kindle Fire a lot after bouncing around multiple games or apps and don’t always remember to shut the screen off, then every 1/2 hour is probably your best setting for conserving battery life.