Really leave it alone.Let it handle things by itself. It will do it itself. You cannot be smarter than Android when it comes to android. Don't Micromanage stuffs.
- Do not Use Smart Manager Features on your device
- Do not Swipe away apps from recent screens except games.
- Do not Force Stop Apps (except some Games)
- Do not Disable Bloatware but avoid using it (Pre-installed apps)
- Auto Reboot Every Monday at 3 a.m.
- Do not Download 3rd Party Apps like Du Battery Saver , they will just kill apps prematurely.
Restarts Kill Battery
Any android app , that runs on your phone needs memory. Memory or RAM is essentially limited . OnePlus Three or The New Galaxy Note 7 might have more RAM. But still it is limited . Sooner or later the app that you ran will be closed when other app needs more RAM. The issue here is that a Full RAM will not take any more battery than when the app is removed from memory and needs to be restarted again. That 'restart' is the real Mother Battery Killer.