Anyone who read "Poor Charlie's Almanack" knows firsthand about Buffett's investment style drift. The younger Buffett was a "cigar butt" type investor who used a geiger counter to look for opportunities. Even Munger makes it clear i his book that this approach netted Buffett something like $300 million.

It was because Buffett kept adapting his investment style that led to the creation of billions at Berkshire. Even Buffett commented on how he didn't want to overpay based on book value for See's Candy and it turned out to be one of his greatest investments.

Buffett is a better investor today because he is a learning machine and has been able to adapt with the times. The value investment landscape is far more competitive than in the 1970's or 1980's , etc.

I like to think of it more as style enhancement than style drift. Buffett is constantly adding to his collection of mental models and expanding his circle of competence.