One therapist I went to was 70, and that was several years ago and I'm pretty sure he's still working. He had retired from one 30-year career (also as a psychologist, but different setting), and was on his second. He knew or met several of the big names in history of this field, and I thought that was impressive. I think more years = more experience = an advantage. But it's important to be current and still learning, too, not stuck in the way things used to be done 30 years ago.