For me they bloom when there is either a temperature fluctuation or if the light levels are higher.
Unfortunately light levels during a temp fluctuation, like in the winter, are lower.
Anyways Phals are very floriferous and can send a spike anytime. I find that lighting is more important than temp fluctuations. I get the most blooms during the summer when because lighting is higher for those windowsill plants. My plants are all sending their spikes right now because of the spring sun
And old spikes can also rebloom and branch, so one spike can get new buds all the time. I have a yellow phal that hasn't stopped blooming for a long time.
For hybrids I don't think I can pin-point a bloom season.