I've noticed for the last few weeks, particularly on Saturday night. We have all gotten used to the big map (whichever of the two arenas it is) having the most people and therefore the most fights. As the night goes along people gradually move over to that thinking that the fights will be there as well.
There seems to be a critical mass point where the number of people on the big map falls below a certain point and it becomes no longer possible to find a fight, even though the arena numbers suggest otherwise. Sometimes its due to 2 of the 3 countries will be fighting off in some far corner of the map so the third can't join in but other times it just seems that people are so spread out they can't really find each other. The milk runners are trying to bomb and take bases without running into anyone which makes the arena effectively a desert.
Just a thought, but as the night progresses, the move should be toward the SMALL map. This would ensure plentiful fights for the entired time. Could be instituted by a call on country or 200 to suggest a move to the small map.