My Samsung S21 was still going strong after 4 years and I charged it to 100%.
My iPhone 12 is about 4 years old. I charge it every night on a Mophie wireless charger on the nightstand. Every morning it’s at 100%. If I use it a lot, it’s down to 40% remaining by noon. It still works well (except of a partially failed speaker for the phone — very low volume).