OK, let me play Devil's Advocate on several points here:
1) not to be preachy, but the very fact that the colony HAS swarm cells points out a lack of space given in a timely fashion; not being judgemental here, just pointing out a problem that we've all unintentionally created at some point, whether caused by inability to get to the colony due to weather, other more pressing concerns, lack of available equipment to give more space, the list could go on for a bit.
There are more factors than just space and management that causes the bees to build swarm cells and other than intense hive manipulation and beekeeper intervention to keep the bees from swarming, some hives will build cells and swarm even though they were cared for in a responsible manner.
Bees want to swarm It is their way of natural survival. They build up in the spring to swarm. Giving the bees the space needed is the first step in swarm control but does not guaranty they will not swarm. there are additional factors. A hive full of bees with little work to do, Many more bees in the hive than what are needed to preform the daily hive duties. Lots of young bees under 3 week old with little to do as the honey flow has not started although there is lots of space once it starts. These bees will start making queen cells cause they have nothing ease to do. How do you manage hives that are places in conditions like this? These condition can differ from year to year depending on weather and temperature and how it effects bee flight and foraging.
The first natural deterrent to the decrease in swarming tendency is when the day begin getting shorter after the summer solstice, but if the bees have already started the swarming process they will continue to raise the cells. Also when the bees get into a good honey flow and all the bees in the hive are kept busy from foragers to house bees and if they are kept with an abundant of extra space to meet their needs raising brood, in ripening nectar and storing honey. They are also less likely to swarm as long as the swarming tendency was kept in check before the flow started.
Some of the most meticulous beekeepers that I know lose a few swarms every year. There are things that us as beekeepers have no control over and how the bees decide to react to what is happening in their environment during those conditions during any given year is out of the beekeepers control.
One of the more popular intense management techniques for swarm control is the Demaree's method of swarm control. Where you let the hive swarm but you move it up in the hive away from the queen so she keeps laying, and the swarm cells can be managed in the top super of the hive, With a replacement queen being raised or nucs made with drawn cells.
For more information on the Demaree's method of swarm control. do a search and there are many variations on how to do it depending on what you want out of it, your hive condition,
