So the Muskrat last day press thingy is just

[DFW]

17. Ya gotta think--if you're 60-ish and have more money than anyone else....

What is left for you to do?

The only thing I can think of is to do something that will put you in the history books. Good or bad, whatever suits your nature.

$250 billion?

First thing I would do is build a big, state-of-the-art cancer research center, and fund it up the wazoo. Biggest, best, brightest minds, all valid ideas considered, grandstanding discouraged, a well-thought-out strategy in place from the start to discourage fraud and waste.
Then, maybe a similar center for heart/stroke disease, a huge division for nanotechnology and micromachines to clear out clogged arteries with minimal invasion.
Lastly, a third such center researching rapid response strategies to new, fast-spreading viruses (ebola, e.g.) with the clout to be allowed on-site anywhere in the world without hindrance or tribute to local warlords.

Allot $50 billion to each project with a $15 billion emergency fund attached to each. That’ll leave about $50 billion left over, but I’m no cure-all, so leave $40 billion for some project I didn’t think of, and leave $10 billion for yourself that you’ll never spend in your lifetime anyway.

I already know Musk’s reaction to my suggestion. It begins with “fuck” and ends with “off,” and has nothing in-between. But that’s why he has $250 billion and I don’t. Sic transit gloria mundi.