G. Mark’s Answer
I've already answered what appeared to be a duplicate of this question. I interpreted it to mean how long does it take to get into a career of psychology. But I realize that it might also be "how long does a career in psychology last?" And I think that is also a valuable question. Bear in mind that "psychology" is a study of human behavior and how to affect it, and that is a very, very rich and complex topic that can only be enhanced by learning and experience. Also, once one has a deep concern for those aspects of humanity, they will usually tend to get better -- unless of course, one gets jaded for some reason -- with time. One may not be able to rush a QB or pole vault as well as one ages, but psychology will tend to get better with experience as one ages. So my personal opinion is that one may decide, for whatever reason, to retire as a professional psychologist or psychiatrist, but this decision would likely be voluntary. So I would not be surprised to see a psychologist, psychiatrist or other counselor be able to contribute well into their very late years.