While I realize there exist extra capacity batteries which greatly extend the G3's operating time, these batteries also typically add to the phone's thickness (to the extent that use of an aftermarket case back is required) and weight.
So I'd rather buy an aftermarket battery of more modest capacity - say, 4000mAh, instead of 6000 - but having the same form factor as the stock 3000mAh battery. True, it wouldn't generally let me go 2 days between charging, but it likely would give me one full day. And that's really all I require from my phone - that I can use it all day long, without it dying on me before bedtime.
I have no idea whether there are legitimate 4000mAh aftermarket batteries out there, which fit in the G3 case without the use of an aftermarket case back. I know that claims of such batteries (and even ones with higher claimed capacity) are readily found on places like eBay. But I take these capacity claims with a moderately large grain of salt. I suspect that in most cases, they're barely as good as the factory 3000 mAh battery, if that.
Still, it's not a horrible problem. A spare 3000mAh battery is cheap. And swapping out a drained battery for a fresh one can be done pretty quickly and easily. No, that's not anything like a perfect solution to the problem, but it's at least a tolerable solution, if only for me.