I was getting what I considered to be reasonable battery life at about 8-10 hours from full to 15%. (At 15% the prompt comes up, giving me a convenient, consistent base for time measurement.) I was playing with my new toy a lot, though.
Since then, I've set up a few widgets to help keep GPS, WiFi & BT off, as well as my screen time out & luminosity very low, and it's really helped.
I've recently dicovered a few things; In another thread, someone mentions to go into the browser and Google home page. Be sure it's in Mobile mode, and in Settings (on the page), uncheck "Always use my location". This (presumably) keeps the browser from initiating your GPS.
Another thing I found out on my own after monitoring my battery usage more often, was that certain apps were presenting a constant drain on my power even though they were "off". -Stupid apps, like a game, and a "find home" type app (even with the GPS, WiFi, etc off). Neither had any means of selecting an exit or cutting resources, and forcing them to close only caused them to cycle back open, so I shitcanned them. One used 4% and the other 2%. I was also a bit suspicious of a game app that is always "on", using 4% of my battery. Kinda strange, I thought.
Maybe we shouldn't necessarily take for granted that an app is well written, or truly off when not in use.
Also, I see an ongoing debate about app killers not being necessary, but this in regards to the system computing resources being bottlenecked from too many apps running. Apparently they won't, but the apps do suck the battery, at least according to the system's power resource graph.
I'm now at 30% battery capacity after 14 hours, 10 minutes. Haven't used it much today, maybe 3 hours total.