Thanks for the further description of your operation.  So the queens are
clipped pre- introduction  to production units - that makes more sense than
the scenario I had imagined.  I had read of British commercial guys (not
operating near the scale you are) going through every colony in the spring
and clipping. It would be ideal to supply a new (clipped) queen at the
beginning of the season as you do; the presence of a new queen is known to
be a big hedge against any swarming anyway.  Small beekeepers like me tend
to let a queen go on for a couple of years or more, and they are sure to
want to swarm that way!
 
It must be nice when you can find the queen on the first try -- BTW, if the
colony is exceptional do you ever save the older queen for possible
breeding, or let her continue in production colony, or is she destroyed
anyway due to age?   Thanks,  JWG