FWIW, I have a 1 year old iPhone 15 Pro Max and its battery capacity is at 98% after 261 cycles.

I too kept mine limited to 80% all year, but not rigorously like Juli Clover… I would occasionally charge mine to 100% when I knew I’d be using it a lot the next day, maybe 4 or 5 times? 🤷‍♂️