During that period, there was a lot of things going on along with him moving his main residence from Persepolis to Mendell City. He took a lot of time off of work because, if I remember correctly, that is when his two children were born. Eventually when he got back to full time, he focused more on his newly acquired rank in the management positions and quickly progressed through those. Mostly, he lost interest in Medical and became more wrapped in with station administration. He is still technically qualified but has not had his Medical licence renewed so he technically cannot be employed as a Medical Doctor/CMO with Nanotrasen. If there was a dire situation aboard the station, I am sure he would be able to at least assist with things but due to his age, he would not be running from one end of the station to another to give medical aid.