Stocks have continued their upward momentum, err, OK, they keep going up. No doubt someday they will get too high and come back down somewhat, but anyone who thinks they can tell you exactly when that day will be is just blowing smoke.
The latest attempt to pinpoint the top is a reference to the CASE Shiller index. Founded by a professor named Shiller, it looks at the Price Earnings ratio, but not the Earnings for the last year, but the average earnings for the last 10 years. It compares this to the historical average, and voila, we are now in a situation where the index is too high. Something like 24 when the historical average is 16 or so, and it was 24 other times when it crashed.
The problem is, stocks don't always crash at 24. Once they went even higher and crashed at 43. In your fear of worrying about a top, you would have missed a 70% run. History is very often a good guide, but situations are never exactly the same. The best advice? Be nimble. Stay invested, but when things look frothy, as they do a bit now, reduce your exposure. Try being 80% invested. You'll have some dry powder if stocks fall, and will still participate if they go up.
You can find the details on CASE by earching it. I love historical perspectives, so I pay attention to this kind of analysis. But, why is 10 years a magic number? If it was 5, the great crash of 2008 would be dropping off now and the index would appear very bullish.