A lot of the old advice really doesn't apply to this phone. I messed with it a lot and now I can get up to 2 days of battery life and I'm on my phone all the time. Playing big Games will deplete it much faster but even if I play Call of Duty for an hour, I can still get over 1 day battery life. I never use limit 85% battery, especially when new, the phone needs to learn your battery capacity. Limiting it won't help it adapt. Also, I noticed my phone would charge to 85% in 20 minutes then slowly charge to the rest. Finally, don't underestimate that 15%! For some reason, if I charge my phone to 100% I get much more battery life than 99%. It will even stay at 100% for quite a while after leaving the charger. My one rule is I never keep the phone on a charger overnight. It charges so quickly there is no need. To prevent apps from eating my battery in the background, I generally keep the phone on Power Saving Mode. Unfortunately, this limits the phone to 60hz (I really wish this was kept separate in the app settings). It makes a huge difference. Without it on, while I am sleeping my phone will lose 15-30% battery. With power saving mode, I lose 1%. I made a Bixby routine to take the phone off power saving mode when I am charging, and this gives my apps a chance to backup and sync when it won't cause problems for me. I also have auto update apps off, and manually update my apps. Try creating different Bixby routines to automate the power hungry settings you might need, so they are on when you need them, and only then. Today, android lets you see exactly which apps are causing the problems so find them and restrict them or limit background data.
