For me, the opposite. $50m is about 100x more than I could ever need, so I'd just stick it in $SPY until I die. Volatility is irrelevant as there is no actual risk to life or limb, only the "risk" of numbers going up or down.
Volatility doesn't seem to have as much power when the potential losses are not great enough to cripple you.
That's precisely why wealthy investors want to minimize volatility. They don't need their wealth to grow (they already have more than they need), but they definitely don't want it to disappear.
Also, I must say that $500k really isn't that much money—it's not even enough to retire.
SPY, QQQ, etc only go up as the economy goes up...