Warren Buffett’s birthday this week was good news for Berkshire Hathaway investors who could celebrate another year of the Oracle of Omaha’s leadership. But the milestone also reminded shareholders they need to think about who will run the evolving company after Buffett is gone.

The more than 80 businesses that Buffett has assembled at Berkshire are mostly humming along well, posting a profit of more than $3 billion in the most-recent quarter. Its Class A stock closed at $127,183 on Thursday — less than $3 away from its 52-week high set in early August.