Fwiw, I have a 13" ThinkPad with a 4k display and get ~4 hours of real battery life or more while working with docker running a handful of containers, browser, vim, spotify, and a few dev tools running.
Nothing amazing by any means, but it's plenty for real world usage and if I stop the docker daemon, I probably gain another hour or two. How often are you working somewhere for more than a few hours without a plug?
My Surface Book has a very nice 13″ 3000×2000 display (28% fewer pixels than 4K). Paired with an i7-6600U CPU and 8GB of RAM, it got 10–13 hours of real battery life when it was new a few years ago—at the time, I think that was not far off being a record for any type of laptop.
I am never going back to 1920×1080. I’m sceptical even of 2560×1440 on a 13″ display. 15″, I’m certainly not going to accept anything meaningfully less than 4K.
