My last game was played til 2052 (on marathon, no less). Julius Caesar and Mansa Musa were tied for first. I fell to third after leading through 2020. But I did build the UN in a last-ditch effort to gain Wonder points, and the game lasted long enough for there to be one secretary of the UN election (which I won), and one shot at a diplomatic victory, with the results posted in 2052. I could only get the support of one other leader though, and Mansa Musa ended the game with a sudden-death time victory.
That was my eighteenth full game of Civ4, all on Noble, and all 18 have ended in a time victory, one way or the other. I think the tech paradigm or productions for spaceship parts is a little faulty, especially on epic & marathon. At least at normal speed I've been an engine away from space victory, but nobody has even come close to the spaceship on those two slow levels. I mean, at least the AI should be able to win if I'm not...