Personally, if the bees are in the winter cluster, I would never, ever even consider to use smoke on them. They need to be undisturbed during their wintertime clustering. Oxalic acid trickling is about the only disturbance that in my eyes is acceptable. When they are smoked, they are disturbed terribly, and like Finsky says, they will break cluster. This in my eyes, again, is not good. This is my opinion and I am stickin' to it.
We smoke the bees to prevent them from flying at us. When they are in the winter cluster, they have no intention of breaking out of their warm little huddle, why would they? Yes, of course you will always have some rogue bees that will break the cluster when alarmed, that is their job, but for the most part, just wear some protective gear if you are worried about the bee stings.
The job of the smoke is to mask the alarm pheromones and also to engage the bees in eating honey. The more smoke, the more honey they eat, and yes, they do eat honey when they are smoked, we have all seen that. The smoke is two fold in its reaction with the bees.
Hmmm.....not too sure where this post was going, just, as I see Ted says so many times, thinking out loud. Maybe more thoughts will come into my mind later. Have a wonderful and beautiful day in this great life. Cindi