I have owned two Tesla's, the recommended is charge to 80-85% regularly and run it down to 20%, reality was I would set the charge limit to 85% and when I was close to 20-30%. Teslas mileage was pretty true the rated miles were what you would get, their battery management was very good. Read the recommendations from Jeff Dahn, tesla's Battery Guru. I wouldn't wait to 20% because you never know what any day would bring, I currently own a Nissan Leaf, (Long Story) the battery management on the car is bad, living in Phoenix on hot days you can count on 50-66% of what the mileage rating is the battery management is poor because it is air cooled, it get me back and forth to work but I charge nightly.
I am hoping Rivian will have good charging control software that can start and stop the charging at a given percentage. I really also am hoping the stated miles are in sync with the actual miles.