There is no exact science, but if the plant was in full bloom in May, it could have been blooming since February or earlier. I suspect you should see a spike starting in December or January. It all really depends on the care. Does this phal need a temp drop to initiate spike? I gave my mom a beautiful white phal with a yellow center that always bloomed amazingly well for us. She grows indoors and for two years, she did not get a spike. I finally convinced her to put it out in her storage shed so that it would get cold (not frozen) and within three weeks she saw the first signs of a spike. It blooms in April and the blooms last for six or seven months at a time.
Best of luck.
Cheers,
BD