My Phalaenopsis orchid has bloomed since last August 2017. When the flowers (always 3) drop off, there are always 3 new buds (in the same location as the flowers that are dropping off) getting ready to open up..usually within a week or so. It has done this three times! It is still blooming now and I see new buds forming again while the flowers are still on the plant. How unusual is this??
This can be quite normal under the perfect conditions. The flowering process is triggered by a photoperiod. This means that when the plants receive more than 12 hours of darkness per day then they will start to flower. This will be common over the winter, as this is the natural process of the sun. This will break soon, though, as we have already crossed the solstice. This means that the daylight hours are increasing, which will soon stop the flowering process. I would be fertilizing weekly with a 1/4 strength orchid fertilizer, by mixing it with water and spraying the entire plant. Roots included. This will give it what it needs for next years flowers.
This is the simplest answer that I can give, as this is, actually, very complex process. But that is the gist of it, anyway.