I had these orchids some time ago and although I cannot tell you how long it took the buds to mature, I will tell you with my first attempt at these beauties, that I lost the buds - they did not open, but would wither and die. The problem that I was having was that I was not providing enough humidity for the buds to mature. I was misting my plant everyday - which apparently was not enough. It was not until I put my orchids on a bed of gravel with a level of water in the bed of gravel and misted my plants, did my buds open. My understanding is that lack of humidity is a very common cause for these flowers not to open.
Best of luck to you - phalaeonopsis orchids have gorgeous flowers.
Depending on the size of the bud stalk it could take a few weeks. The humidity tray is key in helping these orchids stay happy and blooming.My mother in law has several of these orchids and loves them also do not cut off the bud stem after blooming is done you can cut off a third of the length and sometimes it will shoot out a new stalk of blooms to enjoy, the blooms last a good 6-8 weeks sometimes:) HoyaGirl
The flowers can last longer than 6-8 weeks. I bought an Orchid in late August and at Christmas the last flower had dropped. That was 5 months, it was flowering when I bought it, so its 5 months at least. I am itching for another orchid now, I have 2 both of which are flowerless at the moment.