It's really hard to know how long Supreme Court Justices will live. It's true that many will live until their 80s but life expectancy is largely random at micro level. A car crash or some other kind of accident could end the life of a justice prematurely.
With the Supreme Court confirmation process underway, maybe it's time to re-think how we elect US Senators in our country. It doesn't seem right that New York State gets the same number of Senators as Vermont, as New York has 31 times more people then Vermont.
In Reynolds v. Sims, the Supreme Court ruled that State Governments could not have Senate bodies, elected by one Senator per County. Instead, they had to use proportional representation. Maybe it's time for the Supreme Court to consider if the two US Senators for every state (regardless of population) is constitutional.