[G3 Q&A, Help & Troubleshooting] iBolski:
For Task killers, no as per the reasons I listed above. They are battery drainers. They were good a long time ago in the early years of Android, but Google has improved how the Android OS manages resources such that task killers are just not needed for the latest version of the Android OS.

Greenify, it doesn't hurt it, especially from what I have seen. It could help some, and not gain anything for others. My previous phone was a Motorola Droid RAZR HD. With Greenify, I definitely got better battery life. Probably, due to Moto bloat on the phone. But for whatever reason, with the LG G3, the battery life gains are minimal. It appears the G3 already gets excellent battery life so I have stopped using Greenify (even though I paid for it as I felt obligated to reward the developer for an excellent piece of work).

So, I have not been using Greenify or any other battery saving app, save for the Snapdragon Battery Guru app. But even that is minimal in what it is doing. I believe I could probably remove that and still get the life I see right now. I can get close to 2 days battery life as long as I don't play games. That means, doing texting, checking email, reading news, talk/making calls. All of that will allow me to not charge the phone for almost 2 days, but that's never an option. I love playing my games. But still, I can at least have comfort in the fact that even if I play some games and such, I can make it through the day to get my phone to a charger before I go to bed and not fear my battery running out on me. I haven't had that since my RAZR HD running Greenify.

But, it doesn't hurt to use Greenify and for some time, it hasn't required root in order for people to obtain savings, so in the end, it doesn't hurt to use it.

So, test it out. Run Greenify, note what you get, then remove it and see what you get. Or, go the other way. Run without Greenify for awhile, note what type of battery life you get, then try Greenify.

But by all means, avoid task killers. They are bad for battery life and circumvent how Android manages resources.

---------- Post added at 12:57 PM ---------- Previous post was at 12:43 PM ----------

One other thing I wish to add to my first reply. When you bring up the previous apps, you know all those apps it shows that have been launched previously so you can switch to it quickly? Those apps, if written correctly, are NOT running in the background, taking up resources. They are all in a paused state, doing nothing. When you switch to them that way, or launch them from the app drawer, as long as they have not been completely killed of, they will restart at the onResume stage.

So, clearing out that window doesn't necessarily help with performance. Usually, if the phone gets to a state where it's just not responding, it might be time to actually reboot the phone which should clear up some resources. More than likely, it's due to a misbehaving app, not that you have too many apps loaded. But still, it may not hurt to do that once in awhile. However, task killers don't care, so it could be constantly killing apps all the time, which is also not good. Once in awhile can also be a benefit, but it should be selective in what it kills. So, I have chosen to allow the Android system to handle this for me and so far, I have not been disappointed. My LG G3 runs like a dream and usually, within a few weeks, I might have to reboot, but usually, I don't have to. It's been rare that I've had to reboot and only once or twice have I had the phone reboot on me, and usually that's happened after weeks and weeks of not doing anything to clear out the cache and such. usually, it happens after playing a game, such as Game of War, for hours on end without rebooting. Usually, GOW will crash back to the desktop, but I blame that more on GOW and how it's written. Games are very resource and battery intensive, and I'm sure developers try to skirt around some Android development philosophies to try and gain as much of an advantage of performance as possible and that usually can lead to issues.