If you put the town 5 miles from the field, how far will you place the GV spawn object from the town and from the airfield? Will you place down terrain clutter that blocks GV's to the point of making them useless or, will you run time trials from the GV spawn then GV hanger to the town until your average tank say a panzerH gets to the map room in 5, 7, 10 minutes? After all it is a race from two points to the map room from the spawn and the GV hanger. Then will you stop and consider how much time the average player wants to expend driving doing nothing in this game?
If the path to the town is not obstructed and you place the 1x1 town object down with the default terrain editor error test readout minimum requirement. On average the GV hanger will be 2.5 miles from the town center. And a panzerH will take a little over 5 minutes to get there. So if you make it a fair race between tanks, then the M3 will have troops in town in about 3 minutes. It's not really how close the town is to the base as much as which side of the equation you want to favor in the race. The town defenders or the town attackers. I forgot to time trial the M3 until I had laid down all of my spawns 2.5 from town center. Then I had to revisit almost 200 spawns and push the attacker GV spawns back to 3 miles. But then I am carpeting about 6sq miles around the town with village open farm land clutter tiles. On Buzzsaw some of the spawns are past 3 miles with very little cover for GV, and it still took forever to get to the town in an M3 at 50mph. Think of the tank guys how much longer they had to twiddle their thumbs doing nothing when they are paying $14.95 for something.
And tank towns, tank islands, and tank craters, so what. Just make them equally close enough to airbases to mix things up with jabo, bombers, and the fighters that want to take advantage of them from a field 19 miles away. Even airfields at the minimum of 3\4 sector(19miles) will have a higher probability then with 25mile separation of one side of the furball frequently wiping out the other side and getting over their field just in time for a vulch fest. At 17 miles, you guarantee it in spades and hate fests here in the forums like ENY. It's all about the fuel burn an loiter time.