Here’s an interesting little tale:

Bill Gates said the charitable foundation that he set
up with his wife Melinda would spend all its money and be wound up
within 50 years of the death of its last trustee.

In
a move that will add to the debate on whether philanthropic foundations
should live on forever, Mr Gates said the decision was based on his
desire to do "as much as possible as soon as possible".

You see, the thing is that under US law these foundations are an excellent method of passing the money along to the next generation(s) without paying inheritance tax. Indeed, the money gets to sit inside the foundation and earn more, entirely free of capital gains or income taxes. As long as 5% of assets are spent each year, a figure which can and does include paying the family members for managing it, this situation can go on for ever.

As, arguably, it does in cases like those of the Kennedy family and many others. Or the $ 6.7 billion that Warren Buffett put into a family trust (the rest went into the Gates one, as we know). That they are deliberately setting out to exhaust the trust shows that, unlike many suich others, this isn’t what the Gates’ are trying to do. Or, if you prefer, only for a generation or two.