No one in the comment chain claimed otherwise. Breaking changes every rand() * (6 months) is not much better than breaking changes every 1 * (6 months). It still means you have to validate your firewall configs once or twice a year and randomly need to push these changes to network appliances with the same cadence. A key benefit of application stability is not having to constantly read release notes and check if your use case is affected by the changes.
> You have six months to make mostly minor changes to pf.conf before you are out of support. They release every six months and patch the last release.
Yes, they have a schedule for rolling out breaking changes. This is a maintenance burden.
> The changes aren't made for the heck of it, they make a more consistent system overall with new knowledge.
The same is true of many breaking changes in applications and APIs broadly. A cleanly designed system does not magically make the ensuing maintenance burden disappear. We probably all agree that OpenBSD and pf are well designed but we should not ignore its costs.