Let's be honest, if you have a 4:30 report you do need to get to bed at a reasonably early hour. That's the nature of the job and is the case no matter which carrier you work for.
Sky Wave, I agree with much of what you say but the problem can be when you go to bed early but cannot sleep! Not so bad after you've done one or two earlies but can be challenging on the first one.
I think there is also some difference between short term tiredness due to lack of sleep and long term "battle fatigue" caused by weeks of irregular rosters.