Isn't it work until you fall over - then when someone prods you, get up and keep working until you fall over again.
In Oz -no limits, work until you finish - 10 hour break, come back. However companies are becoming more conscious of the duty of care - my joint has a soft limit of 13hrs - any more must be notified to manager for approval - although realistically if you're out in the bush on a breakdown you're gonna keep going.
There was a limit when I worked in NZ where you couldn't certify after 16 hours duty but I can't remember if that was a NZCAA or company limit.
There was a study done in the UK a few years ago which made some recommendations which were pretty strict.
edit: found the link to UK study
http://83.146.40.74/reports/24oct02-...work-hours.pdf