Hi,
Buffett has stated for his wife's inheritance, 10% will be in Treasuries and 90% in S&P 500. He stated that BRK would be OK instead of S&P at a shareholder meeting. Keep in mind, I suspect Mrs Buffett will inherit far more than most of us have in retirement and I further suspect with Buffett's extreme conservatism (i.e no risk of failure), the 10% in cash would last Mrs Buffett's lifetime as it appears to me that she lives a relatively frugal lifestyle like Warren.

Warren has also stated in a Financial Times interview that over 20 years time BRK would perform similarly to S&P 500. Any edge would be small.

All that said, I think that keeping cash for 2-5 years with everything else in BRK is a very fine strategy especially in taxable accounts. But, in Mrs Buffett's case if that means 10 million in cash and 90 million in S&P 500, then most of us are in a different and higher risk situation with that allocation :)

I am trying to figure out for myself how much cash I should keep and I am thinking 2 years expenses is a minimum. I also assume very unreasonable high expenses that I could easily decrease if necessary based on economic conditions (e.g. less big vacation expenses).

Cheers

Brian