Brooks CEO shares the best business advice Warren Buffett ever gave him

Brooks Running CEO Jim Weber has been reading Warren Buffett's annual letters to Berkshire Hathaway shareholders since 1984.

In 2006, the running shoe and apparel company became part of Berkshire Hathaway, when its then parent company,Russell Athletic,was sold to the Omaha-based holding company. In 2012, Berkshire made Brooks a separate business unit. Weber now reports directly to Buffett.

"I was reading Warren religiously starting in the mid 80s," Weber tells CNBC. "The chance to work with him has been amazing."

If Weber had to choose the single best piece of business advice he's received from the billionaire investor, it would be to focus on building the strongest possible brand.

"It sounds cliche, but this long-term thinking about really building a brand of strength is what makes Berkshire so unique, and him so unique," Weber says.

"You can measure brand strength and you can track business results, and they're not always in sync. We all like growth, and bigger businesses are more valuable than smaller ones, but the key is, the brand has to be stronger at the end of the year than at the beginning. And Warren means it. He really means it."

While a lot of people understand the value of a strong brand, not a lot of people understand how brands are built, Weber says.

"Brands are built over years and years and years. And they're built on trust," the Brooks CEO says. "If we're going to do something meaningful here, you can't change who you are every three years. You build a brand over literally a decade, or two or three."