Is the S&P 500 now in a boom-bust cycle?
Here's the Efficient Market Hypothesis (EMH) explanation for why one cannot say that a correction is overdue:

Suppose that it were widely known that, by looking at the above figure, one could ascertain that the market was "due for a drop" one week from now. Financial analysts and investors would look at the graph and come to this conclusion. How would people respond to this knowledge? They would go and sell their stocks before those stocks loose a substantial portion of their value. However, this flurry of selling activity would cause the price of the stocks (and hence the stock index) to fall today—one week earlier than forecast.

This example is obviously a highly simplified and stylised exposition of how markets function, but it should serve to make clear the basic point: any hypothesised means by which one can look at a chart like this and forecast the future movement of prices is automatically self-defeating and any information about the future of the market is instantly built in to the current price of securities. The drop you think might be due will come, says the EMH, if and only if new information about the economy becomes available that suggests the economic outlook is less promising that people had thought.