I used my last phone for about 4 years. At that point the battery life was getting worse, and the coating to prevent smudges and make your finger slide easily had worn off in the middle. Even then it's still perfectly usable, I just wanted an upgrade and to get away from Samsung.

I don't understand the people that upgrade every year or two. In the last 5 years basically the only new development has been higher refresh rate displays and faker looking (more processed) camera images...