Interesting. In my area, Spectrum would give out the same IPv4 address and IPv6 prefix seemingly indefinitely as long as I kept the MAC address and DHCPv6 client DUID the same. It'd persist across DHCP releases and renewals too. Managed to keep my "dynamic" address and prefix for half a decade.

So far, AT&T Fiber is behaving the same here too. I might somehow just be lucky with ISPs :)