When I operated ULR flights the ULR rules applied to flight duty periods. These were fairly complicated and involved such things as having routes approved on city pairs basis, crews established in departure time zones for at least two local nights before flight (IIRC) and departure times strictly controlled to two four hours windows in each 24 hours period to avoid arriving at destination during a double circadian low. Crew rest patterns during the flight were also very controlled and had to be recorded. At that time the maximum duty period was flight time plus three hours. Initially we thought the rest patterns were crazy but it quickly became apparent that they were rather good and I for one always arrived much better rested than when I operated normal long-haul flight where rest was usually split half and half.