Mesix
Obergruppenführer
You shouldn't build cathedrals in your GPFarm.
Your numbers are right. Without Sistine's my GPFarm has around 60 base culture. But any of my cottage cities has never had less than 100 base culture. So, assuming that you don't have 6 cities with 6 temples, there is one city that won't build the cathedral, which should it be, the one that has >100c or the one that has <100c? The one that must stop hiring NE-powered artists or the other one?
Your assumption is what is different. I generally get 6 cities built so that I can build Cathedrials in all three Culture cities. Maybe that is why my games are less successful. If I stay at 4 cities, I would not have to turn down the research slider as far. By the time I stop researching I am generally able to turn the Culture slider up to 80% or more, so maintenance is not an issue in the late game as much (what with Courthouses and all).