I agree. People seems to be blinded by how easily this will be gamed when you know exactly when justices will be forced out. Instead of a roll of a dice on chance deaths from age complications, we’ll get essentially permalocked seats for Democrat or Republican picks to a higher degree than we already do. Justices will likely never serve the full term and instead retire early when under favorable control of the other branches. The chance for a Scalia or Ginsburg swap will happen once in multiple centuries instead of almost every cycle.

Having a firm end date changes the risk calculation enormously to early retirement.