Normal 3 man ULRs are pretty bad, but then consider the max duty limit of 22 hours for ‘irregular ‘ operations!
Two hour delay out of Dubai, maybe a medical diversion enroute, or a diversion at arrival airport, quick refuel and continue to destination, quite easily get up up to 21/22 hours duty limit!
Don't say it will never happen, it already has! 3 man BOS three years back, duty over 20 hours, captain queried the max duty for 3 crew, informed (rather rudely!) that it was 22 hours and to get on with it, or have a meeting with AAR in return to Dubai!
Needless to say, said captain has now moved on to greener pastures!