The general consensus is that once a hive "decides" to swarm it is quite difficult to make it change it's mind.
So whatever you are going to do to prevent swarming sooner is probably better than later - so as to head it off before they go in that direction. At least that is the impression I am under.
This has been touched on in another thread - Simple Effective Swarm Management for Beginners? So - what are the signs to look for that it is time to do something?
Squarepeg said - "walt wright describes looking for a band of 'dry cells' between the brood and the open nectar and pollen. they may appear polished or they may have a very small amount of nectar in them. this indicates that the bees are expanding (opposite of backfilling) the broodnest. it's easy to see even for a beginner. if there are no open cells there, and if the bees are filling cells in the nest after brood emerges instead of getting them ready for more brood then swarm preps are well underway."
Mike Gilmore said - "There is a point prior to swarm prep when they will inspect their colony and find a LOT of new "capped" brood on several frames. The next inspection might find an explosion in population and many of those cells now empty. If at that point they notice some of the brood cells are being backfilled with nectar it's time for them to think about..."
These are both great insights - what other signs can we look for that it is time to take action to try to manage swarming?