When playing in the Sorcerer setting Dictionary of Mu, when you have 20 player-authored demon entries the end of an epoch is triggered. Does this have to be a world-ending meteorite for the game to be a 'real' game of Sorcerer?
Epochs can absolutely be good things. Here's what I am saying. I am not saying the GM should decide what the next epoch means. I am saying you end the game with the player having taken over Black Rock and killed Nimrote. The GM does not then do something catastrophic in order to end the epoch unless it comes organically out of play. You end the session, do advancement and base the next epochal changes to Marr'd based on the players next kicker. Does that make sense?
I wouldn't say it has to be world-ending, it just has to be appropriately large that one or more of the player's kickers play a significant development in how the world changes.
On pg. 142 of Dictionary of Mu it says that the end of the an epoch is "defined by the player's kickers."
So I think it certainly could involve an end-of-the-world condition, but I think the more general form is just one of immense change based on the driving force(s) behind the character's individual stories.