Dozy.........Maybe you can't sleep well during the day coz you only work 2 nights. This is my point, I think that the first and the last night on have gotta be the worst, the first coz your knackered and the last coz you want an easy night as your off tomorrow. Only working 2 nights, you only work the first and last. I think the middle 2 of four nights you will be at your most efficient.