Couple of different things... Here we go:
-Snapdragon Battery Guru. Set all apps to "Refresh only when used". Turn on the data off when screen off option. Wifi management is optional imo, don't know what kinda effect that has.
-Alternatively, you could turn on power saving mode. CPU only. You CAN NOT use this and Guru at the same time, fyi
-Auto brightness on all the time. You could download an app like Lux, setting the autobrightness a little lower than stock and going with that for even more savings. But I find that stock auto is smoother
-GPS off
-Only the network location enabled
-Sync off
-Watch apps in general, make sure nothing obnoxious is constantly running/refreshing
-Haptic feedback off
-Disable any bloat via app manager
-Download an app like Wake Lock Detector to see if anything is causing wakelocks and deal with it. Facebook messenger is a big culprit, for example. I uninstalled that.
That should do it for most. 7 hours screen on time is definitely possible, perhaps pushing 8. Should be easy to get 6+.