Christians (including the apostles) have been proclaiming the end of the world since the very early days of the church. Jesus' return, and the apocalypse He'd bring, was expected within a generation of His resurrection.
Children, it is the last hour; and just as you heard that antichrist is coming, even now many antichrists have appeared; from this we know that it is the last hour.
—1 John 2:18
But the end of the world hasn't yet come, despite the many dire predictions of mainstream and splinter groups over these last two thousand years. Most Christian groups have now wised up and stay well out of the prediction game, but some still swear it's going to happen any day now (next prediction for the end of the world is May 21, 2011).
The fact that the original church was wrong on this profoundly important point, and that many generally accepted as legitimate (as well as wacky) derivations of the original church have been wrong about this profoundly important point, makes me question how right they can be right about the less important issues.