There is an natural time limit based on the game speed you set it on. You can still continue playing after that time limit but your score no longer goes up.(similar to a time victory in Civ IV)
I think on the standard speed its 1000 turns.
+ The game now ends at 1000 turns (modified by the game pace). Players have the option to continue playing but their score wont be recorded after this point.
p.s. Fancy seeing you here
