the fundamental rule is once started bees will not tear down cells even under some of the most unusual conditions.
tecumseh, I must be misunderstanding something here. Bees build and tear down queen cells all the time. We have one hive that seems to keep a queen cell or two in reserve, constantly building the cells, capping them, and then tearing them out. Either these bees are in a constant state of indecision about swarming or they are just playing it safe as far as possible supercedure. If you mean that they won't stop once they are committed to swarm, that may be right... but how do you know when they have committed? Building a queen cell is clearly not the signal, since they reverse that all the time.
And where does this 30 day number come in? I can't say I've ever read or heard that bees make a decision 30 days in advance. And how could you know the 30 day clock had started unless there is a clear signal? Opening the brood nest and checkerboarding have been reported to be successful in reducing swarm behavior. Does opening the brood nest force a reversal of a 30 day swarm decision? How could you know without a signal that a decision had been made? What is that signal?