Dont expect to hear day-to-day criticism of President Donald Trump from Warren Buffett.

Even though he campaigned last year for Trumps Democratic challenger, Hillary Clinton, Buffett said on Monday that he isnt up for regular fault-finding with the Republican president.

There isnt much reason to, Buffett said in a brief interview after appearing on a cable TV show. Hes going to be president for four years. You want him to succeed.

If you want a different president, Buffett said, you get a chance every four years.

But he said on CNBCs Squawk Box business program that its generally not a good idea to quickly respond to criticism via Twitter or email, as Trump occasionally does.

It really is a mistake to give an instant reaction to everything that comes along, Buffett said.

His Squawk Box session was at the event center in the Nebraska Furniture Mart store. The Mart is owned by Berkshire Hathaway Inc., of which Buffett is chairman and chief executive.

It was the 10th year that Buffett has appeared on the three-hour morning program to discuss his yearly shareholder reports, which are widely read for his comments on investing, business and other topics. Berkshire posted the 2016 report on Saturday.

During the program, Buffett said he would judge Trumps performance as president by how safe the country remains, how much his policies help the U.S. economy grow and how widespread the benefits of that growth will be.

Asked whether he would vote for Trump in 2020, Buffett said, Well, it depends on who he is running against. I would say it would be unlikely.

He said he generally follows two rules for commenting on people publicly: praise by name but criticize by group; and wait until tomorrow to criticize because your viewpoint often changes.

Buffett also said his investment ideas dont coincide with his politics: If you mix your investments with politics, youre making a big mistake. I dont think that makes sense.

He revealed that Berkshire more than doubled its investment in Apple Inc. in January, from 61 million shares at the end of 2016 to 133 million shares today. He stopped buying when the stock price rose after Apple reported better-than-expected 2016 profits.

Berkshires $18 billion worth of Apple stock, about 2.5 percent of the company, is its second-largest stock investment behind Wells Fargo Bank. That doesnt count $28 billion worth of Kraft Heinz, which is owned more indirectly.

Unless other stock buyers have changed, Berkshire would be Apples fifth-largest shareholder, behind investment firms Vanguard, 6.43 percent; BlackRock, 4.22 percent; State Street, 4.19 percent; and FMR, 3.01 percent, according to Yahoo Finance.

Buffett said he likes Apples future.

Its quite a sticky product, he said, which means people tend to buy new iPhones to replace their old ones and to buy other Apple products once they own their first one.

Although he uses a dumb flip-phone himself, Buffett said he watches his grandchildren using iPhones when he takes them to Dairy Queen on the weekends.

It gets built into their lives, he said. They barely can talk to me. ... The continuity of the product is huge.

He said Tim Cook has done a terrific job since becoming Apple CEO in 2011.

Buffett said he decided to invest in Delta, Southwest and United Continental Airlines, while Berkshires American Airlines investment was done by one of his investment lieutenants, whom he did not name.

Ted Weschler is known for being interested in American Airlines. As Berkshire investment officers, he and Todd Combs each invest $10 billion of its money.

Buffett said the airline industry had a bad first century. They got that century out of the way, I hope, and now they are more profitable because the supply of airplane seats is closer to the demand.

Buffett also said:

Smart people and billions of dollars are focused on self-driving cars, which will become more commonplace as long as they are safe. Auto insurers like Berkshires Geico division will lose financially as accidents and insurance rates decline.

The Dow Jones Industrial Average, a measure of the stock markets growth, eventually will reach 100,000 from todays 20,837. The figure is a calculation based on the prices of some leading publicly traded stocks.

U.S. stocks are on the cheap side at todays interest rates and, as a group, will gain in value over the coming 10 or 20 years, even though he doesnt know what will happen tomorrow.

The stock market is not in bubble territory, meaning not in danger of a collapse in stock values due to excessive prices.

An import tax, discussed by President Trump for Mexican-made goods to pay for a U.S. border wall, would be a sales tax. Of the Marts $400 million in goods sold each year, 75 percent are imported and consumers would pay the tax.

Free trade is wonderful for the world and the United States but can be terrible for specific industries and their employees. The government should help people who become roadkill when imports destroy domestic industries.

The United States has led the world in productivity and growth for the past 240 years thanks to a market system that frees up people to reach their potential, immigrants who provide manpower and ideas, and protection by the rule of law.

The Omaha World-Herald is owned by Berkshire Hathaway Inc., 402-444-1080,