More like 3. I had the 6S, and Apple had a deal that ran out on December 31 that year where they would replace the battery for $29.95. My battery was showing 75 or 80% still, but I decided a new battery would let me keep it at least another couple years, and about all the new ones were larger. So I got the battery and kept the phone until the new SE came out.What do you mean, “nothing wrong with the old one”? ! The damn batteries fail after two years !
For a lot of folks, maybe most, the reason for upgrading the phone is to get a better camera. If I want a better camera, I buy a new camera. The new reason to upgrade the phone is to get 5G. I spend so much of my life in range of wifi that I don't see any benefit to me of 5G. And no matter how fast my phone is, I don't talk any faster.