The game tracks every character ever born. No, really. Every character ever, even those who are in the history files dead has to be checked for events and various conditions for every in game day. When a character dies they are still stored in the history files, and the game continues to track their progress until the end of the game at 1453. It doesn't matter that they are dead, the game is still tracking them.
Whow, this is odd. Even those who are long dead.
Does this mean that the savegame file is getting huge over time?