One concern I would have would be molds growing in the media-
I hadn't even considered this. Very good point on why some people (like my wife) can't handle orchids en masse. Too much perfume and maybe a touch of mold to kick off those allergies!! lol
Molds can be a problem for many people with allergies. I have some of my orchids is s/h and I don't get mold with this method of growing. I think whenever possible it might be good to change your medium once a year, or when it begins to break down.