as airsupport pointed out shifts of 24 hours in duration
Actually I did not say that exactly, I have NEVER been rostered for a 24 hour long SHIFT, that would obviously NOT be legal.
Just that is how it has worked out, many times a scheduled check or rectifications have gone on much longer than "planned", and then although I was sometimes literally falling asleep on my feet, have had to keep going as there was nobody else there that could release the aircraft.
I have been flying with Pilots that have had to go slightly over their ''normal'' limits to complete a flight in progress, but nothing like is expected of LAMEs.
I will never understand why there is NO hard limit for LAMEs, even if was say a ridiculous figure of maybe 20 or even 24 hours straight.