My last Sony phone as a daily driver was my Z3. Battery was fine on that until I did anything that made the CPU go into meltdown.
On the XZ Premium, Sony and Qualcomm have got things nicely under control - which means the phone doesn't run too hot (which in itself plays havoc with the battery, and can make it near impossible to charge) - and the battery doesn't seem to take much of a hit even when playing video or taking photos.
My phone can still get hot when taking photos and give me the warning, but despite me using the phone heavily, the battery (given its size) works commendably. Especially if you enable any of the stamina modes
I could live with most of these modes enabled all the time, with the only issue being when using an on-screen keyboard (it missing characters pressed), and then the battery lasts even longer.
tl;dr - the battery is good and I'm very impressed. You should get a whole day of usage without fear, and with a good deal of screen-on-time.