Maybe they need to turn off the double tap for s-voice so it doesn't have a delay when you hit the home button. If you do not, it will always have a half second delay between pressing home and going to the home screen because it's waiting to see if you double press for s-voice. Then reduce animations to .5x.
These two things helped a ton.
I consider this pretty good for real world battery life. Over 6 hours screen on (auto brightness), and over 15 hours off the charger until it dropped to 1%.
That is the best battery life I've ever seen anyone get on a Samsung phone ever. What is the typical screen brightness? You said auto-brightness but what was it most of the time? Rooted with tweaks? Custom kernel? Wifi the entire time? I wouldn't call that "great" but in my experience pretty impressive for a Samsung phone. From what I've seen that is FAR FAR better than the Galaxy S4 battery life.
I had to dig back to what this was about - and it was your comment that once you lose one-hand ability, you might as well go as big as you can. I was simply trying to illustrate that there's another threshold around pocketability that phablets can cross. The Note 3, G3, and G Pro 2 are on the right side of the threshold, IMO the One Maxx, Mega 6.3, and Z Ultra are on the wrong side of the threshold.
I guess I forgot to mention pocketability. I meant to. Any phone that loses one hand usability also tends to not be pocketable either, at least not comfortably. Even my Nexus 5 without the case isn't comfortable to carry in my front pocket and I don't even where tight pants. I actually buy carpenter pants so I can use the side pocket on the right leg for my phone. I would go nuts if I had to carry my phone in my front pocket.
That's not a very scientific way to measure battery life. I've owned a G2 and in general, I'd say other owners on xda find battery life to be quite good and on par, if not better, than the Note 3. Battery life threads on xda at least have a sample size of hundreds of users, if not thousands.
Every phone will have problematic users - there are Note 3 owners on xda who can't get 3 hours of on screen time for whatever reason.
That is XDA. How many of those people had rooted phones with a custom ROM, custom kernel, under clocked CPU/GPU, etc?
Sure, the examples aren't the best but they were the only ones I could find at the time. I'm not saying the G2 has terrible battery life but far from what I would call great from what I've read since it came out.
There is also the test I personally did with two different G2s in stores shortly after it came out. I admit it isn't the perfect test but it did give at least some indication of what would be the average expected battery life.
I tested with the following conditions: unplugged the phone at 100%, brightness at a comfortable level of about 60%, wifi on but not connected, location on, bluetooth on. I used the phone for 30 minutes doing a verity of things from streaming video(YouTube and Netflix), streaming audio(pandora), browsing and a bit of game playing(about 5 minutes). At the end of that 30 minutes the battery was down to 94%. Based on that battery drain if I had continued to use it the same way until the battery had died it would have lasted about 7.5 hours and that is constant usage so no stand by time. That is a discharge rate of about 15% per hour on average. If I had stopped after 5 hours of usage(which I would consider pretty good but not great) the battery likely would have been at about 25%. That would have resulted in an overall off charger time of about 20 hours with 5 hours of screen on time under what I would call normal usage. Of course that isn't a "scientific" test but it is a real usage test using rough calculations and at least a decent estimation on what I would actual expect owning one.
I also know 2 people that own one and tend to get a little closer to what you see from the Google search I did. My best guess is that the coverage at the stores I went to was better than their typical average daily coverage.
From the reviews I have read the G3 gets noticeably lower battery life which is expected considering the slightly bigger display and the 1.78x as many pixels with the same size battery as the G2.