I've done a few playthroughs with different groups of people and people seem to start burning out and getting tired around the same point. the late bronze age and whole iron age seems to be a gap of new stuff to do and those are the ages said groups of players usually start falling apart. beyond that my friends on average loved the game but without new challenges to tackle or new stuff to do they started to lose interest. some lasted longer cause they took up building but even they eventually stopped playing. hopefully new content can be added to the late bronze, iron, and even steel age. OH also the steel making process seems to be intimidating to new players, it seemed alright for me whose played a few times but for players that it was there first run through they seemed to almost avoid the idea of setting up the steel process, my best guess is they feel like they shouldn't bother if they cant get the best bricks but I don't know for certain.