Hi Boo, the “preemptive” part of it means you try to get in before they start making preparations to swarm. If you can do that, you’ll be right for a few weeks as long as you do what I do & remove most of the sealed brood when taking the split. Taking the sealed brood is the main key because you’re removing all the new bees that would have emerged over the next 10 or twelve days. That puts an instant stop to the population growth, coupled with fresh foundation frames the colony has to rebuild, that postpones the colonies desire to swarm for at least 3 weeks. While the population growth has been temporarily halted, natural mortality will still occur within the colony, adding weight to the fact that the bees wont swarm for a few weeks.
In the mean time, while the colony is rebuilding the brood frames, the bees that were producing honey will continue to do so…
While this is happening, I like to use a single brood box with a single honey super, however I try to keep the honey super from getting full of bees. I like to keep it at about 75-80%, which gives the bees room to expand into, coupled with the hive mat & migratory lid.
As soon as I see bees in the migratory lid building up & doing nothing, or even if the honey super looks full of bees, I’ll think about a preemptive swarm control split.