Not 4x4 nights but financial circumstances forced me to work permanent nights for two years a long while ago. It is very exhausting. No matter how you try, it is impossible to avoid the "jet-lag" and the constant fatigue is probably very harmful to your health. The effects may not show for years but it cannot do you any good to be permanently knackered like that. I blame my current heart disease on that spell of permanent nights.
My advice is - if you can possibly avoid it DON"T DO IT!
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Through difficulties to the cinema