I have cable at home. I've had the same "dynamic" IPv4 address for 3 years, which is how long I've lived here. It has persisted multiple power-losses, some extended. On the other hand I get a new IPv6 prefix at least once a month, including every power-cycle of the modem and/or router.

I don't know if this is related but I've seen isps that put you behind a cgnat over ipv4 if you have ipv6 connectivity but they give you an ipv4 ip address just for you if you disable ipv6.