There a many people taking up law now that probably have aspirations of one day becoming a judge. It can be a long and tedious road, but with hard work and the right knowhow, it's not improbable to imagine quite a few of these students eventually attaining judgeship, one of the pinnacles of a law career. But even after scaling that mountain, the journey hardly stops there. Indeed, judgeship could be considered an exciting new chapter instead of the end of a journey.
However, there will come a time when even judges need to slow down. That is more or less inevitable; one cannot compete with Father Time in the end. Now, the mandatory age of retirement will depend on the state the judge serves in, but most states have a mandatory age ranging between seventy to seventy-five years old. Vermont, on the other hand, has a retirement age of ninety, whereas a few others have no mandatory retirement age at all. And even then, these mandatory retirement ages are typically for state courts. For judges working for the federal courts, their lifetime appointment by the President and confirmation by the United States Senate means they can stay on the bench for the rest of their lives.
For those who are allowed to retire, there are several things they can do. First of all, not all who "retire" from being a judge actually end up retiring for good. There are some that still wish to continue their professional lives, so it would not be a stretch to imagine them finding some way to continue working, regardless of whatever it is that they may want to do now. Some embark on totally new careers. Then there are others who may wish to completely leave their work lives behind them. In this way, they are free to pursue other passions that may personally sustain and fulfill them until the end of their days. Basically, whatever floats their boat.
So to answer the question of what judges do when they have to retire, the answer would vary quite a bit. One can say that some don’t. So long as they are capable, they will serve, in some capacity, for life. One can say that they go back to doing what they were doing before. Or they leave their legal careers behind altogether. And no one would be able to call those answers inaccurate.