Stocks are in a "secular bull market" that's going to last many more years, veteran portfolio manager Martin Sass told CNBC on Thursday. But there will be corrections along the way, he warned.
Investors should not try to trade the pullbacks "because one doesn't know when that's going to happen or when you get back," the M.D. Sass CEO said in a "Squawk Box" interview. The boutique investment firm has $6 billion under management.
If anything, buy into the dips, he said. "The big picture is stay invested in good, sound, undervalued companies and there will be a lot of money to be made over the next several years."
Sass said the dovish Janet Yellen—if confirmed for the top job at the Federal Reserve—would lead a push "around the world of central banks fighting deflation, stimulating growth, injecting continued monetary accommodation that allows ... an eight-year expansion, at least, in the economy and the stock market."
One of the triggers that could lead to a correction: the Fed starting to scale back its $85-billion-a-month bond-buying program. "If I had to put a bet on it, I'd say March is the meeting they'd start the tapering," Sass predicted.