If I might add one word of wisdom from my personal experience, even if isn't from this site necessarily.

What keeps a game alive is not IC but OCC. If people are excited about the game and chatting constantly in OOC either about the game or just with each other they remain invested in it. And such a game can survive a lot, even people vanishing for a long while. But if the OOC is quiet and people are only ever posting IC odds are good that any significant delay or drop in the post rate will kill the game dead.