Some methods I personally use to extend the battery life of my phone (1) which is almost 2 years old now and still gets me 6-7 hours SOT. Do note that I’m not a heavy user.
Change refresh rate to 60 hz
Disable auto brightness
Enable dark mode
Disable Wifi/bluetooth Scanning under location services
Disable RAM expansion feature
Enable smart 5G in network settings
Never let the battery drop below 30 percent and ideally below 50.
Always use the nothing charger and remove any case/cover while charging if possible.
Hope this helps!