Yesterday I came back home after a two week absence. Although I had someone water my orchids one week ago, they received no care for the last week that I was away. Most of my orchids looked perfectly fine, if a little dried out when I got home. The phal in the top left picture had a few droopy leaves, and the oncidium on the right was perhaps more wrinkled than when I had left (it's roots had grown, however).
Meanwhile, many orchids showed signs of great growth. The phal in the middle picture has added at least half an inch of length to its roots, as did my angraecum leonis (whose leaves became slightly more wrinkled, but with no other sign of dehydration). The keikis on the big phal have grown bigger than ever. For others of my orchids, there was barely any change at all, except for slightly droopier leaves. This includes my paphs, oncidiums and the cattleya. Even the paph sanderianum (my most expensive, and supposedly delicate orchid) weathered the dryness without any sign of trouble.
I did notice that my slc scheherezade had lost a root over these last two weeks. However, since orchids usually lose roots due to overwatering, I don't have an explanation for why this one rotted away during a dry period. Perhaps the watering it received a week ago was too soon for its needs, or perhaps the random loss of a root is not something I can ever find a reason for. The leaves and pseudobulbs on the cattleya look fine as ever, so I'm not overly concerned.
The one orchid that really did suffer from the dryness seems to be my dendrobium victoria reginae. This is a wet-growing orchid, which I ordinarily water every couple of days. It is one of the few orchids whose media I never allow to fully dry out. I found that 3 leaves on the dendrobium's newest growth had dried out. Also the lowest leaf on the old growth looks like it's about to fall as well.
The discoloration and visible veins on this leaf indicate that it has started an irreversible dying process. At the same time, even though lost leaves are never pleasant, I am not too concerned about the survival of the plant just yet. Leaves can always grow back.
Ultimately, my regular houseplants showed far greater signs of stress than any of my orchids did. If ever I need a reminder that orchids don't need to stay wet, this is it.