Warren would have been better off buying back stock at opportune moments the whole time

But this applies to ALL companies that performed better than the average S&P500 (if the S&P500 return is the comparison). Look at Apple for example.

Does this suggest that Buffett has been over - optimizing BRK buybacks?

I understand the logic that buybacks should only be made when below a conservative estimate of IV. But do the potential "overbuys" outweigh waiting too long to do buybacks when they still outperform the alternates?

I don't have the data to answer this. But I suspect BRK has spent a helluva lot longer being undervalued than overvalued.

Especially when the alternative is holding cash for extended periods?

Not a criticism. Just an honest question about which would perform better over the long run?

Probably impossible to answer. It would all depend upon what alternates for the cash showed up better than BRK over the cycles?

We don't seem to have found many of these recently.