I agree with Martok and Poor Bloody Infantry.

Most strategy games do have setbacks when world conquest is concerned. It's fun to get big and fight for your survival, but once your too big, you become unstopable. Basically its fun to have a challange not a cake walk. At least mtw2 adds the mongol and timurid invasions. Distance to capital penalty, and religious differances also play a part to increase the late game challange.

It would be nice if rebels were active and related to these penalties. This would seem to add to the challange of maintaining a large empire, but maybe it would just add more unwanted micromanagement. The problem in mtw2 is not so much the lack of challange as it is the scope of world conquest, which can be a very long task. Its made longer for me because I don't use auto-calc for battles. In most of my late games, there are still battles to be won, lands to be conquered. I just don't have the time to do it all.

Lack of time, lack of intrest, lack of challange, and game frustations, are the reasons I have never completed a campaign. They are the same reasons I abandon my campaign, the game, and these forums. I get bored with other games too, and thats why I am back into mtw2 trying to finish a campaign by conquering the world.