The key is to keep it in between 40-80% as much as possible. Ideally around 65% all of the time but that’s impossible. Don’t ever let it discharge below 20%.
This used to be me and I am SO glad to be over it.
1. An iPhone battery will last all but the most extreme users 2 years before it hits 80% and needs replacing.
2. Plenty of people baby their phones and see a capacity loss, while people like my wife abuse their phones and still have great capacity (93% on a launch day x)
It’s just not worth it, at all. A new battery is cheap, and you will get 2-3 years out of your stock one. By then I would assume most people will upgrade. If you want 5 years from a phone, get a new battery after 2.5 years and then once 5 years hits and the battery is shot, just trash the phone and upgrade.