I hate to tell everyone this but there is no such thing as "new blood."  It's an illusion invented by each generation so as to look down on their predecessors.  Human beings stay pretty much the same, with a few cultural tweaks here and there that cycle (what was hip to your grandparents was old hat to your parents and is hip to you) and of course we do evolve, but that takes millions of years.

I read Socratic dialogues and have no difficulty, separated a whole world and several thousand years from them, fully understanding their motives and humor and relationships and so on.  Part of that no doubt is Plato's genius, but still it tells me people everywhere and every-when are pretty much the same.

We do not need new people every generation (although I must say I like children so a world without them would be lacking) to keep things fresh.  We just need seriously enforced term limits.