In 2019, I attended Project Horseshoe and participated in a workgroup dedicated to developing a rulebook for creating stories that are not designed to end (such as for games as a service, live games, etc.)

The whitepaper based on our workgroup topic has been published on the Project Horseshoe Reports page! The whitepaper is called “Everlasting Narrative:
Developing a Rulebook for the Theory and Practice for Creating Never-Ending Narrative in Games“.