It also matters how active the cluster is. If you look at bees in the winter, in the North where is stays cold, you'll see that different colonies cluster differently. Some form tight clusters and are so quiet that you'd think they were dead. Others are loose and humming loudly.
I think that those colonies that have the ability to withstand long periods without cleansing flights are the colonies that maintain tight, quiet clusters.
Many things will cause the cluster to break and the bees to be actice. Mice in the hive or a branch scraping against the hive all winter will. Tracheal mite infestation will. Sugar on the cluster will. Nosema will. Bad genetics will.
Long winters with no cleansing flights take their toll on our bees. Those not able to fly at least a couple times in their 5 month confinement suffer the worst damage. Here in Vermont, when we have a winter like that, there will often be a few days that are almost a cleansing day. Bright, sunny, calm, and just a bit too cold.
That's where wrapping in black tar paper helps the most. After an almost flight day, you'll see that the wrapped bees have flown out in front of the hives, and returned home. There are no dead bees or yellow poop stains anywhere 10 feet or more away from the hives. In a 4' wide strip in front of the rows of hives is the evidence. The bees were able to fly out in front because of the slightly elevated temperatures in and around the hives. They cleans, and are able to safely return to the entrance. When the sun begins to fade, and the temps drop, they reform their cluster.
Where I keep bees, that alone makes wrapping worth the time.