Sometimes, one case where I made use of this is enumeration of uarch for different hardware to read from the host machine. The update for for new uarch type is closed ended until there is new cpu with new uarch, which is long time. So, for a very long time it is open-ended with very low velocity in change. It is ideal for enums (for a very long time), but you still need to support the change in list of enum variants to not break semver.