100 cities / turn We're hoping to keep empires from reaching such insane sizes...I personally hope a HUGE, sprawling, glorious empire never grows larger than 20-25 settlements. But that's just me
But, if you have 32 races, and then say 10 minor races, 20-25 cities is obviously too small. Assuming that you spread out some before going to war, and establish, say, four cities, then at four a piece you have 128 cities, just for the main races. Plus say another five or six for the minor races. Let's just say 135 for ease of computations.
So, if you're a huge sprawling empire by turn 500, and have crushed a few players, you probably have say, 40 cities, pretty easily. I don't know about you guys, but I wouldn't want to create 20 vassal cities and try and stay friendly with them. Unless they were puppets, forced into trade with me of course.
Assuming you win by conquering your foes, you should pretty easily have 80 or more cities, if not closer to the 135 total. Both numbers are of course, well above 20-25.
EDIT: Qouted the wrong person the first time, also, sorry for the double post, I seemed to have gotten excited.