Izzie,
Mold vegetative cells (and most mold spores) are killed at well below boiling temperatures. All mold spores that I can recall are easily killed at boiling temperatures.
I have been doing the "soak and plant" for about three years now. I have had problems, but I do not think even sterilization would have prevented them, because of how I grow - outdoors in SW Florida. We are surrounded by mold, and (I think) any attempt to eradicate it leads down a path of increasing chemical use and weaker plants. When I have had a slightly more serious problem than a small spot on a leaf, I do use Daconil spray. It doesn't cure the problem, but it lets me feel I've done something until the leaf ages and falls off.
The problems I have had are directly related to choosing a medium that will hold too little or too much water in my part of the world. Indoors where you are in total control of watering you can eliminate many uncertainties.
Again, just my opinion, but I think orchids are beautiful and rugged plants, designed to live in a dirty moldy world. If you let them be, they will adapt and survive. If you change their conditions too often, they never adapt and they get weaker. Example - today I repotted two phals that have lived outside since 2002 (guessing - it was before my recordkeeping started). They were inexpensive Costco Noids. I was so inexperienced when I got them, I didn't know about pot hangers, and I wired them up with copper electrical wire. They were still in their original clay pots with a plastic pot inside. Over these rainy and dry seasons they hung in a large guava bush and received marginal care. Even today they both had active nodes on a couple of spikes. The original media had almost rotted away and been replaced by roots, and the roots had filled the space between the pots and had circumnavigated the pots many times over. There was evidence that on one or two occasions they had been stressed (root "centers" without the surrounding tissue, which had rotted with the media). They hadn't been repotted for so long because they always seemed to either be in bloom or in spike. If I had had the knowledge to respond to every stress and attack, I question whether they would have given nearly the joy they did for these past years. I've attached pics (I hope) of before the repot, after extricating the roots, looking up into the root ball, and after the repot.
Obviously, everyones situation is different. If I were a grower or competitor, those who judge would have frowned on my plants. As someone who wants to look out my kitchen window and smile, with as few headaches and as little work as possible - it works for me.
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Dry heat, boiling, mold, and too much care
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