[Knufen]

I have a One+ and I can't really recommend Greenify (App) enough. Forces all apps to shutdown, even those running in the background.

[com2kid]

I have plenty of memory, I don't want apps force closed.

If I switch from a game to a browser to look something up, being able to switch back to the (paused) game 5 minutes later is a feature, not a bug.

Apps that obey backgrounding and stop doing work (e.g. burning CPU/Power) are fine.