there are a lot of variables when it comes to battery life. some days, my phone makes it through the whole day and then around 12 the next day it dies. other days i find myself looking for a charger before i get home from work (around 9pm)I fall into the later camp, my SE has been horrible since updating to iOS 11, Apple even replaced it under warranty and still its crap even after setting up as a new phone.
Then you have others who come along "Oh my phones great, runs even better than 10.3" I can't understand it. It's not my phone as that's been replaced, it's not my apps as I only have 6 non Apple apps installed at this stage the only thing it can be is iOS. My phone runs fine its battery life that's taken a major hit, I used to get a full day and until about 6pm the following day with my usage on 10.3.3, On all versions of iOS 11 I will not make it past 9pm. Not even a full days usage.
it really depends on your usage, battery capacity remaining and charging habits. And when i say usage, i don’t just mean how long you used your phone, because 30 mins of gaming doesn’t equal 30 mins of web browsing.