Would it be cheaper in the long run to buy a newer phone less often? Get a "this year flagship" and use it for 5 years rather than a couple year old model and use it for 2-3?
I don't think so, this was the first time it happened like that.
No. You get a 2 year old flagship phone for $200-300 outright, instead of $1500+
Samsung also makes the A-series Galaxies which are a pretty solid mid-tier phones that are supported for years, too.
A flagship is ~1000, a good enough phone is ~200. So, no.