[WillAdams]

I maintained such a schedule for over a year when I was in the Air Force --- the schedule was 9 days on, 3 swings, followed by 3 mids, followed by 3 day shifts, then 3 days off --- extending one's sleep cycle to a longer "day" allowed one to make things fit together w/o too much disruption.

That said, avoiding having to do that again was a big motivation in getting out.