[Baalz]

I think the biggest factor, much more than length of game, is static-ness of borders. Doesn't matter near as much how long the game goes on, what matters is how long your dominion has effected the provinces you hold. If you're an aggressive player and more or less constantly expanding (or less optimistic - trading provinces) then a good portion of your kingdom is always freshly under your dominion (or still under an enemies) so hasn't had time for that exponential growth. If your borders are fairly stable and your dominion covers most of your territories, you'll see much more of an effect from growth/death.

Personally, I wouldn't take death and misfortune unless you're playing a nation/strategy not reliant on income from population (like LA Ermor).