Sucks he has to quit because of that. I had a brush with it years ago, I fell asleep with headphones on. I then woke up in the middle of the night with my ears ringing. Turns out I bumped the portable CD player volume wheel in my sleep to MAX. I am a heavy sleeper so I was listening to full volume music for what could have been nearly the entire album (think it was AC/DC or Sabbath.) It took hours to subside and during that time I was scared, "Did I just accidentally give myself hearing damage?". The next day I told someone and they said "You're lucky it didn't cause permanent damage as that is what tinnitus is like 24-7." Never used headphones in my sleep again and wear ear plugs to concerts. Must be an awful thing to live with.
