The problem is lack of map rotation?
The requirement for 40% of the other sides' fields is a gigantic hill to climb on a small map. It often requires a "leap" across an area of uncapturable fields. It's not impossible to do, just very difficult. Super horde can do it with discipline. It is similar to the problem we have just overcome with the larger towns and old capture system.
To increase the map turnover rate is a very simple fix for HTC. All they have to do is reduce the required target to be less than the current 40%. Try 35%, if that doesn't work then try 30%.
I don't know of any absolute metric that can quantify the point when play on a map becomes boring. Gut feeling says about 3 days. A straw poll might give some sort community reflection on how long a map is in use before it gets stale.
Given that there will always be tougher maps and easier maps there will not be a perfect answer. Right now, in off hours arena, 40% is too high.
