And my iPhone 6 (cannot recall when I got it - but it was new and the latest at the time) still - bizarrely - shows 100% max capacity. Admittedly, I use it sparingly, no social media, just phone, texts, a little browsing sometimes, a hotspot sometimes and a small number of apps (e.g. weather, calculator) and it is turned off every night, but 100%? I’d like to believe it but it seems non-plausible. Nevertheless, I am happy and, like you, have no intention of replacing it until/unless it dies.