Here is how I have it set up- I have three cooltubes (600, 400, 600 all HPS) (the one hanging in the center is a 400MH, I had an extra ballast so I threw it in there) with one 6 inch inline fan pulling outside air on as long as the lights are on and blows it outside. I also have a room thermostat that when ambient temps reach 83 degrees-all kinds of fans kick in- another 6 inch inline kicks in, and another blows outside air into the room and two five inchers up in the ceiling blow out through the roof.
In the clone/veg/mother room I just have a 4 inch that pulls air from outside and blows it to the flower room when it gets to 80.
This setup will be sooooo much easier than waiting till all have matured before moving in the new batch. Now I can keep a steady flow to keep my distributor happy. Plus then It seems like not so long of a wait if I can cut about every two to three weeks.