Ideally, keeping it between 20-80% will prevent unnecessary wear and tear due to the additional heat and stress at either end of the spectrum. Charging always slows particularly at the stage of topping it off, so unless I know that I’m going to need extended hours away from a charger, I don’t commonly try to go above 90% much. A few times doesn’t hurt anything, but regular use that drops below 20, or above 80 is definitely not fantastic for lithium ion chemistry.
Anyone is welcome to take or leave that advice. I’m technically not an electrical engineer, but I have spent a few years working with BMS (battery management system) design for various lithium battery chemistries, and these principles generally hold true for current battery styles, until we get to true solid state, or alternate chemistries (sodium ion is less energy dense, but more resilient, and less prone to combustion, for instance).
I sure miss the days of user replaceable cell phone batteries. When I had my LG G4 I would just buy one or two extra batteries and a charger for that battery and always have a fresh battery waiting for when my phone was about dead and just pop in a fresh battery. I almost never had a cord attached to my phone and it was wonderful!