Warren Buffett is cashing in stocks like Apple because he knows the good times won't last but he'll spend big once disaster strikes, a veteran strategist says.

"He is selling out of one of the most overvalued stock markets in history at the 'high' and once there is a serious correction or recession, I am sure he will, as he always does, start redeploying those assets back into the market at much lower prices," Paul Dietrich told Business Insider.

B. Riley Wealth Management's chief investment strategist was referring to Buffett's Berkshire Hathaway selling more than $17 billion of stocks on a net basis last quarter - its biggest three-month disposal in years.

Berkshire offloaded 13% of its monster stake in Apple, which accounted for virtually all the sales.

The conglomerate's disposals fueled a $21 billion increase in its stack of cash and Treasurys to a record $189 billion. Buffett predicted the money mountain would exceed $200 billion by the end of June.

#buythedip