Ticks keep ticking even when the other half of the world is sleeping
You can go 12 hour ticks but then the game moves so slow very few will keep an interest. Unless you an automate doing something during the when you are away.
I like turns everyone gets the same and it's how you use those turns that makes the better player. Course you have to have a limit to the amount of turns you can save / bank so someone doesn't come in the end of the game cycle and win but that is pretty easy to do.
Always remember not everyone who is playing will be playing in the same time zone as you.. On State of Crime 80% of my player's are in Europe, I'm in the US so I have to be VERY careful about time sensitive things in the game.
