I am thinking of taking the hit and getting rid of my Galaxy S6 for the LG G4. The lag and having to reboot every few days is unacceptable. Hard to believe with all of the high end specs of the S6 it runs like crap
It's funny but reading your post word by words sounded just like the G4 I returned after just 8 days and 3 factory reset, but mine also had an average battery life, definitely less than my S6 Edge.
After returning it I decided to get an S6 to be the couple to my S6 Edge, best devices I've had in my life, lag free and an excellent battery life. Currently at 40% on my S6 after 29 hours unplugged and 3 hours 10 minutes of SoT, no power saving mode option and location on in battery saver mode.
As you can see everybody's experience is different but after my 2 S6, and 4 more that I've helped set, (2 of my co-workers and 2 family members) with the 6 having similar results in battery life and performance I can honestly say that if you do some or all the tweaks I've posted in my thread and you don't get a defective device, this is the best Android phone ever made.