If you think about the enormity, the sheer magnitude of evil against the victims of the Nazis what else are we to do. True justice is utterly impossible for humans to obtain for them. All we can do is keep hunting down the guilty until none are left. Don't let them rest. We can't.
Yes, the world should continue to prosecute Nazi war criminals, as time does not erase the stain against justice that these terrible people committed. During World War II, 8 million Jews were slaughtered. Genocide does not simply go away because time has passed, so these Nazi war criminals should be charged and tried wherever found.
No matter how much time has passed, if a living war criminal, from Nazi Germany no less, is still alive and breathing and has not faced justice, it is an injustice to the rest of us. The fact that Nazis were not only allowed to get away, but hidden by various world governments, set a terrible precedent to people everywhere, that if you are a war criminal, but valuable, you will be protected. So we must proecute them, not out of vengence, but out of justice.