He may speak very well, but he'll also need to maintain that skill. You don't have to focus on free conversation. Select topics on current events or points of interest for him to discuss, debate, or give presentations on. He can always learn new vocabulary, work on intonation, etc.
I've written an article on advanced students, which may be of help. You can find it here:
Advanced English Lessons | Heads Up English | ESL Lessons