The work requirement and days off etc etc would all be spelled out in the employment agreement, no? Or doesn't this company have employment agreements? There would have to be an employment agreement as part of the work permit application process, unless the pilots are working under the radar on a tourist visa?
And there would be a fatigue management system as part of the ops spec, no?
Unless you're on equal time tours you can't work 7 days straight, or whatever the rule is. If I didn't fly on a particular day for whatever reason I'd write that down as a day off. In all my years in PNG I don't ever remember an instance of a helicopter not flying when there was a job to do because the pilot was on a day off. Even on bases where there was only one pilot and one helicopter.