I'd think about investing in birth-control pills, or at least the companies that make them.
And private accounts for Social Security start looking much more attractive as well!
Can you imagine these 70 year old billionaires if they had another 700 years to multiply their fortune?
They would own the solar system, maybe the Milky Way; the Hubble volume would take a little longer.
In fact, I wonder if they aren't really 70 at all, but maybe 140 and just say they are 70 to put us off our guard and make us think they are just too smart for us.