I move mine to mats at 12 months (once they can walk and climb, it is more dangerous than helpful to have them in a crib IMHO).
I keep my youngest on one side of the room and sit in the floor between them. They are all usually out in about 10 minutes or so.... (that being said I only keep 6 with 3 being under 6 months. It will always be "work", and no two days are exactly the same
Some days are just better than others. I also play the same quiet time cd, and use a boxfan for white noise everyday.)