I owned an iPhone 7 for 7 years. For the last 2 years it stopped getting the annual iOS updates, but other than that it worked great.
So from date of first release, it seems that a typical,iPhone should last at least 7 years. Some people still use older phone like the 6S today.
That means an iPhone SE 2020 should last until at least 2027, perhaps a year or two longer than that?