There are a lot of references in the internet with using heat to treat Varroa in large scales. Those services are too expensive for the hobbyist because the set up alone is expensive. What I have seen are devices that hold hundreds of frames at the same time and heats them, for what I thought 20 minutes. Not sure where the hour comes from. Also, not sure why we don't do it here but it may relate to the fact that we like simpler methods.
The heat treatment methods I have seen being sold here don't really provide a good solution because they do not heat the hive correctly. Some areas get too hot and some not hot enough. The entire hive needs to reach 104 degrees for just a few minutes in frames with brood. I am not a scientist but if I remember correctly, 108 and the larvae begins to die. They are not affected at 104. I actually looked into bringing in a system (heats frames only) from Germany that will handle 30 frames at a time but the cost was about 1K plus 600 to ship and I could not find many people around here who would be willing to share some of the cost.
