A Weak Sauce Argument Against Aged Justices

In today's NYT:

You may have heard that justices and other federal judges enjoy "life tenure" — something that is easy to believe when the average age of the Supreme Court justices is 69. However, Article III of the Constitution says only that federal judges, both of the Supreme Court and of lower courts, can retain their offices as long as they maintain "good behavior."

This seems to imply that the justices have a duty to retire when they are no longer fit to work full time.

Wait - how exactly does one make the inferential leap from a standard of good behavior to a mandate to retire when old?

But as the influence of the court expanded in the second half of the 20th century, that practice seemed to disappear. Some justices, even those seriously unfit, have held on to their awesome power and status long beyond what was reasonable. William Rehnquist, who continued to work on cases in 2005 even as he was dying of cancer, is the most recent example. The celebrated Thurgood Marshall, who was 82 when he retired in 1991, was another.

As long as Rehnquist was putting out sane material from home in his final days, what was the problem - how was he not on 'good behavior' - ?  And the phenomenon of ancient justices is not of late 20th Century vintage.  Oliver Wendell Holmes, Jr. was on the court until the age of 90 in the 1932 - and he continued to produce influential jurisprudence until that time.  The improved medical technology of today and the overall longer average lifespan also contextualize the presence of any additional older justices.

Overall, Professor Carrington's op-ed royally confuses good behavior, casting a slower pace or a medical setback as stand-ins for "bad behavior."  The tone is eerily reminiscent of FDR during his attempt to pack the high court in 1937:

When I commenced to review the situation with the problem squarely before me, I came by a process of elimination to the conclusion that, short of amendments, the only method which was clearly constitutional, and would at the same time carry out other much needed reforms, was to infuse new blood into all our courts. We must have men worthy and equipped to carry out impartial justice. But, at the same time, we must have judges who will bring to the courts a present-day sense of the Constitution - judges who will retain in the courts the judicial functions of a court, and reject the legislative powers which the courts have today assumed.

Ironically, FDR worked from this statement, which blunts the central distinction of Carrington's piece:

But all federal judges, once appointed, can, if they choose, hold office for life, no matter how old they may get to be.