Re: The BEST queens are mated after the Solstice...
I've had very good results with queens mated in late June through early August. They lay well for winter then come into spring fully ready for a honey flow. Swarming tendency is significantly reduced.
Daniel, the issue re commercially reared queens is that the queen producer needs thousands of drones to properly mate the number of queens they raise. They also need good weather for the queen to fly. Between low numbers of drones in early spring and poor flying conditions, many queens get shipped that are not properly mated. There have been a few studies on this, the last I remember was written up about 20 years ago.
NW Alabama, 46 years, 24 colonies and growing, sideliner, treatment free since 2005, 14 frame square Dadant broodnest