Why kill apps? I’m an Android developer. A top tier Android developer. And I ask you, why would you kill apps? Your reasoning for killing apps to save battery life is irrational and illogical. It’s impossible for an app designer to accommodate their app being killed in most instances! Killing an app can potentially cause the app to not work especially if the app is dependent on services and broadcast receivers registered in the manifest.
Conclusions: Unless your a developer, or a power use DO NOT KILL APPS!
If you don’t like the app, or the app is causing a problem UNINSTALL IT, REMOVE IT, but DO NOT KILL IT unless you fully understand that you can be causing the device and the application to malfunction.