But isnt the point of the game? Ability to replay? Try different things. Start at different places on the planet. Set goals at what is you own "end game".
In the case of CK2, play a family story? I have over 1300 hours on that game, all with the 769 start and never went over year 1000. Also having the most memorable moments as a gamer, many of which were either maniac evil laughing in the middle of the night of the acts the devilspawn Doge of Amalfi executes against the Pope. To tears due to the life and fate of your character who started playing from the age of 3 as a simple Count to his death at the age of 43, prevailing to unify Ireland crown himself King and forming the Kingdom even for 2 days, while having dark luck fallen on him with all the negative events the game has. Ending blind, castrated, one handed, one legged and disease driven during his adulthood, while managed to survive numerous assassination attempts at the younger ages even from his mother.