Mississippi homeowners — what’s the oldest AC unit you’ve seen still running?

I work in marketing for a local HVAC company down here, and I’ve noticed something interesting.

In Mississippi heat + humidity, most systems we see start struggling around year 12–15.

But every now and then… someone has a 20+ year old unit still kicking.

Is it just maintenance? Luck? Brand quality?

Curious what y’all are seeing around the state.