why? To spread the good genetics?
Drones have a few uses .
One is to improve the genetic pool in the area, whether one has drones or not a VQ will still fly off to a mating congregating area.
So it matters not if the colony has 100 or 1000 drones.
Harmony within the colony is another reason.
Having drones or excess drones isn't as some seem to think a precursor to
'oh they are going to swarm' , I have colonies that don't swarm and they have many 100's of drones.
Swarming is often mitigated by by many other factors and not drones.
Selection of raising Q's from less swarming stocks is a starting point to try and improve one's lot, open mating is always a gamble but flooding the local area to try and dilute bad genes may help.
Q age sometimes can play a part but I have a 2021 Q that the colony are happy with, again sometimes can be down to selecting from your less swarmy colonies.
Laying space and stores clogging early on can be one of the main factors for swarming.
Trying to keep bees to a single national with very productive Q's is simply choosing the correct system for them. If they need double brood for space then that is what they need.
Use colonies for selection that superscede.
If a colony produces 10's & 10's of QC's then don't propogate from them.