Why would anyone want to play more then 18? The more civilizations are in play, the more difficult it is to keep track of them all. You then waste time having to check on them and remember every one of them instead of concentrating on the game and your own cities...I generally find 8 civilizations enough for me, I even find it fun with as little as 5. Make the most out of who you have, then you get to get personal with them.