I remember playing CK1 that after 200 years have passed, the number of characters goes up in the game exponentially and eventually would cripple the speed of the game. So while it used to take 30 seconds to pass a month (on medium game speed), it eventually would take 2 minutes go through a month. Not only that, the game also becomes laggy that would make it unplayable for weaker systems. 
Is CK2 designed differently to prevent this from happening?
Is CK2 designed differently to prevent this from happening?