I never added the night cycle actually, it was just added by someone else who edited the map. The problem with it is that first of all it causes lag because the lighting changes all the time, and second it starts to get boring or look ugly to most people after they see it several times. The game looks better in daylight, and it's easier to tell units apart. The night cycle would be a good idea on an RPG-type map where there is some part of the story that happens at night or in a dark place than on an "instant action" map.