I'll add some data. Here's a modern era game.
18 units, 108 maintenance
17 units, 95 maintenance
15 units, 81 maintenance
13 units, 69 maintenance
11 units, 56 maintenance
9 units, 44 maintenance
7 units, 31 maintenance
5 units, 20 maintenance
3 units, 9 maintenance
1 unit, 0 maintenance
edit: This game was on prince normal sized map normal speed.
18 units, 108 maintenance
17 units, 95 maintenance
15 units, 81 maintenance
13 units, 69 maintenance
11 units, 56 maintenance
9 units, 44 maintenance
7 units, 31 maintenance
5 units, 20 maintenance
3 units, 9 maintenance
1 unit, 0 maintenance
edit: This game was on prince normal sized map normal speed.