Well in my opinion I think it's quite simple, do flowers help an orchid grow or hinder it? Are they an energy source or an energy sink? Flowers have no chlorophyll, they take up a lot of energy to bloom, so no doubt they would use up more energy than they could possibly produce.
So cutting off an old spike could be nothing but good for the orchid's growth. I think if you want better flowers next year, cutting off old spikes is a good idea.
Just ask farmers who grow Phalaenopsis and Cymbidiums for the cut flower market. Do they cut off old stalks that couldn't be sold? I'm sure they do.
The only reason you would leave an old stalk on the plant is if you want more flowers NOW! but for the period that those extra flowers bloom you're not going to see much new growth and the plant would be set back a while.
Of course if you REALLY want good flowers in a particular year, cut off ANY spikes in the previous year and put all that energy into better spikes the next year.
That's also what commercial cut flower growers do when they get first-flowerings on immature plants. They don't want the small one or two flowers that come with the first flowering, so they cut off any new spikes until the plants are 5 years mature, meaning their plants grow faster.
Interestingly, i HAVE read a paper (just recently) that looked at the purpose of aerial roots and whether or not it was better to cut them off or leave them be. They concluded that they expended slightly more energy than they gain from photosynthesis or water/nutrient absorption from the air. Therefore they recommended you direct them back into the mix or cut them off entirely.
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