That inflexible and uniform adherence to the rights of the Constitution, and of individuals, which we perceive to be indispensable in the courts of justice, can certainly not be expected from judges who hold their offices by a temporary commission. Periodical appointments, however regulated, or by whomsoever made, would, in some way or other, be fatal to their necessary independence.
This statement offers insight and answers for my prior speculations regarding how the weakest branch would not be forced to be politically conjoined to the more powerful branches. The lifetime tenure ensures that the justices would not have to adhere to the needs of the offices that allowed their position in the Court.