I believe some of the fractional operators have some potentially long, fatiguing duty days, however knowing that there are a myriad of factors which effect fatigue (age, sleep conditions, allergies, lack of adequate food, crossing of multiple time zones in consecutive days, heck even personal motivation) they have an iron-clad, no questions asked, no retribution style fatigue policy. Essentially a crew member can, for any reason, call fatigued. They are pay protected and more importantly, "fatigue protected."
As fatigue affect each person differently, a one size fits all policy, whether based on scientific data or not, will not completely eliminate it from the cockpit. If a policy doesn't completely eliminate or significantly reduce fatigue, how can it be acceptable for the passengers?
People like to argue that scope is the most important item in contract talks. Maybe, but imo, having an iron clad policy to eliminate fatigue and increase safety should be near the top of the list. It may not be sexy, but....