I just plugged my phone into the charger. But it was up and running all day, over 18 hours, with 2 hours of screen on time, and the battery was down to a bit over 50%. I have the AOD turned off, run the screen brightness on auto, trained to be sort of low, but very readable. I consider this to be fine battery life. Theoretically, I could run for 36 hours with 4 hours of screen-on time to get down to zero battery power if that pattern holds true.
But there are a lot of variables.
For example: If you are in an area with low signal strength for the cell system, then the transmitter in the phone adjusts its power upwards to compensate because the signal path is, of course, the same in both directions. So that eats battery faster. The same may be true for WiFi, but I'm not sure.
I leave my GPS off, don't have bluetooth on, etc.
But I have power saving switched off, and run the screen in the highest resolution. So I could take steps to reduce power use a lot further. But I've seen no need, since the battery has been holding up just fine.
I did no factory reset after the Oreo upgrade, but I did clear the cache. I guess I feel lucky and have no complaints before or after Oreo.