This paper grows from research which focuses on the learning characteristics of PhD students, incorporating communities of practice both during their studies and beyond completion of their PhD, and drawing on theories of adult learning and lifelong learning. It shows how professional discourse enhances academic discourse through student engagement in lifelong learning, and how PhD "learners as field experts" turn into researchers beyond their PhD, influencing their environment and contributing to academic culture and society. We present these insights as a model of adult learning and professional development.