well if this temp theory is true it sure did not help the feral bees that was inside a thick tree trunk with only an opening the size of a silver dollar.
Another anecdotal response. That is like saying wearing a seatbelt didn't help the guy who died going off a cliff when his brakes failed. Unless you know what was the demise of said colony, and the other issues involved, your are just using your bias in judgment.
The ferals around here are booming. I know others on the forum have strong feral populations as well. All the survivor stock (been in the location for more than 1 year) that I have removed have sealed up every little hole in the cavity except the entrances.
So I believe it helps with the varroa mites that naturally fall off the bees. I do not know if the temperature differences between open SBB and closed SBB make any difference in mite population. Maybe it doesn't matter either way.
Or maybe it does. Maybe the mites that naturally fall off are insignificant compared to the increase of mites that are raised in the cooler/drier environment. You can easily get the so-called "advantages" of SBB mite separation without taking the heat away.
It amazes me some of the hoops people will jump through to be "more natural" in their beekeeping but will just ignore, or justify to themselves it is not important, that the natural temperature/humidity aspects of feral colonies. I don't know if it is just "we know better", the human need for visual stimulation, or we are just sheep to what others believe. My experience has shown me that heat definitely plays a big role in a hive. I admit it is not "the answer" and I don't know the full extent, but I'm not willing to discount it. The bees seem to think it is important, and despite all our knowledge, I tend to believe them more than man. When I put a 7 watt night light on the bottom board, the queen will move right down above the light to lay. Hives that I heat build up faster in the spring than those that I don't.
Here is an interesting read on nest scent and heat -> http://forum.beemaster.com/index.php/topic,17318.0.html
Sometimes I just wonder if we are just cutting the nose off to spite the face. My ancestors where fishermen and I can remember my grand dad telling me that when they clammed and caught a star fish, they would cut it up to kill it, because star fish eat clams, and throw it back into the water. What they didn't realize was that each piece would regenerate and they where actually increasing the star fish population.