I worked for years on 12 hr crewing shifts without a break. But then again I worked with a great team of Crewing and Ops people, and the aircrew where a great bunch as well, it was great fun and I enjoyed every minute of it, and we had the tightest UK operation imaginable.
Our rapport with crew was excellent, we understood their problems and they understood ours and the company really did benefit. Crew were always given as many personal requests as operationally possible to help with their disruptive lifestyle. And overall this arrangement worked very well when we had to call back the favours.
This great team of people has recently been torn apart by a recent merger, if only the current managemnt of this "new" airline realise what they have missed.
:o