If I followed his advice the last two years I would have missed a big market move up!
Yes, talk to the people who were making money hand over fist in Nasdaq during the Internet boom for several years. Or talk to the people flipping houses and making money hand over fist during the housing boom before 2010, for a decade. Our private golf club had dozens of new members join, most were in housing business.
Any mania does not end suddenly. Greed always exceeds prudence. I do not know the date on which bear market will begin. It could be 2 months, 2 quarters, 2 years or 2 decades. Only thing I can guarantee is it will be painful for those caught holding the bag.