I’m running a 3 year old flagship phone (As it happens an iPhone). It’s still blazing fast, still has great cameras, still got the latest os and the battery health is still in the high-80s percentage range which is plenty for a days use. I don’t see any compelling reason at all to change my phone (more compelling is a £60 battery replacement when the battery does start to fail to win another years life) and I bet many others like me are in the same boat.