How long will this bull market in stocks last?

The "bull market for stocks is 94 months old, making it the second-longest in modern history" according to Jason Zweig, writing in The Wall Street Journal, Jan. 21, 2017. In his weekly "Intelligent Investor" column Zweig explains the results of recent research showing that investors are affected by the optimism of other investors, often resulting in poor decisions. Investor optimism indices have increased recently. Zweig explains: "New research shows that the confidence of others can influence your decisions even more than your own experience can. At a time when stocks and bonds alike are expensive, investors need to be even more vigilant than usual against the risk of getting stampeded by other people’s emotions." (emphasis added). Now seems like a good time to reblance one's portfolio and if you need cash, do like I've been doing, sell your winners and lock in those gains. This bull market will NOT last forever.
"Confidence is contagious. But acting on it can be dangerous." (Zweig)