I'm not the guy that upgrades clubs regularly, but 20 year old equipment seems a bit too long for me.
That said, if you hit something very well, there's no sense in changing.
I really liked the CG16 irons I bought used for $300, but the shafts started breaking. So, I replaced them with my current set of Mizuno JPX-EZ from around 2015. So, they're 10 years old. I bought them used from a friend for $400.
How often do you play?