This is arguably the actual secret to Berkshire Hathaway's long-term market-beating success, although there's one detail here that needs to be drawn out.And yet, Berkshire enjoys all the flexibility that neither fund managers nor private equity firms fully enjoy. That's the flexibility to do both, either, or neither, or even do nothing at all; as of the latest quarterly report, Berkshire holds $340 billion in cash just waiting to be invested in something. Buffett's in no hurry either. He's just waiting for ...