Truthfully, I don't really know how else to conserve water but by reusing it. I have quite a few plants and to toss the water after every plant (and what? Bleach the bucket each time?) would just be too costly and wasteful. We have a water softener and the water just isn't good for plants. I collect rain water and buy distilled water so I don't like to waste the water.
Dunking and dumping does seem awfully wasteful. To water the mounted plants I have in my seedling nursery, I use a pump-up sprayer, which is far more conservative.
Folks who grow mounted plants should consider potting them, as that will extend the drying time.
I'll also throw out there that we all have choices, and if water conservation ranks higher in one's individual priorities than the health of the orchids, maybe orchid-growing isn't appropriate.