I leave most of them on, the only one I have ALWAYS off, is space race. I like to keep in control of my game, and play as long as I please (while still being scored). I hate the space race, because the AI always builds it, and it FORCES me to build it or loose. I don't like that concept. I could take over their Civ, but I like to keep a world balance. Its just my type of game. Histograph victory all the way!