During the fiasco called Kavanaugh one of the Left pundits (I didn't take notes, but this isn't a unique assertion) allowed has how the USofA is the last modern country which puts its supreme court judges on the bench for the rest of their lives. He also allowed that an 18 year term has been broached, and he supported such. The argument is simply that a life term in 1800 spanned far fewer years than today. That's not disputable. But what is disputable is how much? The pundit stated 36 as the life expectancy then, while now it's around 75. Lifetime appointment is nuts!!!! And so on.
But, naturally, it's a somewhat bogus argument. Life expectancy at birth didn't change by big numbers until the 20th century. Childhood vaccinations, sulfa drugs, antibiotics, and such account for why folks live longer. And most of the increase comes before 21 or so. Here's a succinct table.
So, yes lifetime Supreme Court appointment is nonsense, but not because middle aged white men live a whole lot longer now than in 1800. Another table which indicates about 8 years more now for 50 year olds, a reasonable guesstimate.
So yes, Kavanaugh is a horrid candidate (and should be impeached for lying at his 2004 and 2006 hearings), but he'd not be around as much longer as the "life expectancy has risen 40 years since the Constitution" assertion. Don't use stupid numbers to make your case.