Every market period cycles. This one will as well. In the early 1990s it was unbelievable that the market would ever go down. It did. In 2006/7 same idea. Everything's great. Average guy had no idea what was going on in the financial world. Then boom it was over. Same today, we don't know exactly what will cause the boom to end but something will or a combination of things will occur to cause a crash. Here where I live is all it takes to start the domino effect is something that stops or slows new construction and the perception that it will get even slower.
