From my point of view Beetle, the "closer fields" allow people to STOP the steamroller, or at least fight back. What I see, personally, is that on ALL maps now the only way the "front" moves is when one side applies overwhelming numbers. On most of our maps that works great (actually, it works great on all of our maps). What typically happens is that you'll see 40 or 50 planes attacking an undefended base, while penny-packets of 3 or 4 move on to the next 2-3 bases to pork the fuel to keep a fight from developing.
If the bases were closer together (say 12 miles instead of the typical 25 to 50 miles), the defenders would have more options as far as defending the fields go. The attackers would have to pork the fuel at say 6 bases instead of 2 to ensure that nobody would be willing to fight back at their original "target". Would this lead to more "la7 conveyor belts"? Of course. But that isn't a function of the fields being closer together, it is a function of what planes people are willing to fly. It doesn't matter how close the fields are, you are never going to see a conveyor belt of Spit 1's or c202's.