The Dredd RPG I run dealt with the issue of Dredd's rejuve directly (I'm going to kill him off). Rejuve treatment for someone of Dredd's age is spectacularly expensive and subject to the law of diminishing returns. He will require more expensive treatments more often as he gets older and the probability of degenerative failure increases over time.
So, in the version if MC1 I RPG in, Dredd is a significant budget header for Justice Dept. He's a symbol, and the council of five underwrite the expense. They simply don't do it for other, less storied judges.
In my RPG, Dredd is starting to show signs that the degeneration is kicking in. There are also the crop of younger judges who think HE is part of the problem; he's a throwback to an era that is over. The infallibility of the judge system has been disproved and they are starting to ask the question: Are we actually the best for MC1 or do we need to start preparing the ground for a return to some sort of democracy?
Anyway....my two cents.