Well I am now very close to winning for the first time. Though I am tempted to prolong the game by rebelling against my Sovereign. He owns 3/4s of China and at least half that land I took. I think he's getting smart though, I used to run over 25 of his cities as viceroy and had 50+ Generals under my command. Now I'm down to 5 or so and he has split the rest up among other generals.
That's the best time to rebel. What's the point of winning if you're under the service of somebody else? :-D It's benign to conquer China for a powerful overlord; it's exhilarating to take it away from him!