I never called safety of flight, but probably should have on several occasions. The one thing I never did/do was pass up an opportunity to "rest your eyes." If there's a bunk and you're augmented, there should always be someone in it. One of the many mistakes I made was joking to my crew about "wake me up before we land." We were flying from Okinawa to Elmendorf, and 9 hours later, those dipshit LTs woke me up on approach-- just in time to cuddle up to a stripper at the ABC. Calling safety of flight shouldn't be a difficult decision, but then I didn't fear reprisal because I was lucky enough to actually have leadership that backed up my decisions. I'm guessing that's where this so called "difficulty" comes into play. However, when I DID made a decision that may have been questionable, I always gave a courtesy call back to the sqdn before a grenade got rolled into the CC's office at 0700.