I agree that we are at a time when battery life should be prioritized, but I would prefer that to come from thickness. Increasing the thickness by just 25% or so would allow a much larger battery.
Obviously there's a cost to this, both in battery and hardware requirements to push those extra pixels. Meanwhile nobody can detect pixels on a Nexus 5, but apparently it wasn't good enough.
And next year we'll see PPI at 500-600. I just don't get it.
As for thickness, I think the Nexus does quite well. It's about 50% thicker than the iPhone 6 which is a great number (~10mm) to be at in my opinion.
Yet we use smartphones...
Anyhow, my Nexus 5 lasts the day, I plug it in at night. That's good enough. And I like the screen.
Battery life only matters to a point - after that features and niceties matter more...
Second, there is such thing as a 'good enough' battery. For most people, this has been achieved with the current crop of big screen, high res phones.
Not sure why you think people would accept lower resolution for an extra half hour of battery life...