My experience of bmi longhaul is that after a meal and lights out one of the cabin crew comes round every 30 minutes or so with some OJ and water on a tray for anyone who wishes to take one. Hence those sleeping are not disturbed unnecessarily, and waking pax get the opportunity to see that the CC aren't skiving, so everyone is happy. It would appear to also give a number of the crew a chance for a break as they weren't all involved at the same time.