I for one would not trust my eternal future to word of mouth story telling over centuries.
Not many people would. Even most of the other religions in the world, past and present, have what they call "Sacred" writings. It's as though nobody DOES trust what gets handed down "verbally" especially if it spans centuries. That's not to say, of course, that all those "other" writings are anywhere near the same league as the Bible, but I think something tells us not to trust other people's musings. Satan tries to use this tendency to his advantage, of course, as he does anything else that is truly from God, and he perverts and counterfeits what God has established. That is especially why God has provided us with the Bible so that we have an infallible and authoritative source for the truth of the Christian faith. He does not leave us at the whim of men to verbally tell us what God tells us, but establishes his word that does not fail nor pass away.