You can go with that phone easily 3 or 4 years ..most phones now go a long ways .. especially now that security updates are longer ...on this forum we have plenty peeps like me that upgrade regularly even if it's just small updates from year to year ...personal choices ..
I had an S10+ that was still working fine. The only reason I upgraded to the S22 Ultra is because of the trade in offer and the free accessory offer. My S10+ was 2½ years old and still completely functional without any lag or battery issues.
Do you need a new TV every year, or a new laptop? Perhaps a new car annually?
My point is no you don't need a new phone unless you enjoy spending the money to have the newest device all the time. My Verizon Note 8 just got a software update for a security patch, still has full app support, runs fine, and that thing is over 4 years old at this point.
Bottom line is do what your wallet can afford. If you're into gadgets, awesome. If you're more practical, nothing wrong with that either. Like others have said, updates are around for a few generations, so you'll have a few years under your belt.