How Long Does It Take to Play Through Old World?

Civ 4, Civ 5 games tend to be about 20 hours. Sid didn't sit down and decide that he wanted the game to be 500 turns long. The reason he did that is just because there are a number of like distinct eras in world history which you can't skip overnight. So for sure with old world, I'm trying to figure out a way to like kind of like do just the first half of the game. Like that's my hope.