I play games by "turns". One month (or what it takes) I play, let's say, Civilization III from the begining to the end, and then I play another one, and so on, and later I play again the games I have played before. I include in this rutine all the Civilization games, Age of Empires II, Empire Earth, Pharaoh, Zeus Master of Olimpus, Tropico, Star Wars Galactic Battlegrounds, etc. Good games such as Alpha Centauri (wich I consider a Civilization Game) are games I will play again and will not let get dust.
By the way, I never play multiplayer games with this type of games. Multiplayer is fun for a game such as Unreal, where the game lust for some minutes. Those great games I take my time to think each movement, some I must save and resume for days, and it would be very boring to play against another one like me.
By the way, how many years old is Alpha Centauri?