Just my opinion here: I dont mind the occasional loooong day (16 hrs is extreme), what fatigues me most however is 8 hrs from gate to gate. Nothing like 12 hrs duty followed by one hour to get checked in, one hour to get dinner and wind down, 5 hours of sleep, one hour to get ready for the van time (no time for a good breakfast here, besides its 4 am, where am I gonna eat at this hour??) and another 12 hour duty day again today to make me the most tired. MIN 10 hours BEHIND THE DOOR is what I need to be safe!