While researching my switch from PC's to T5's, I had mentioned to a Tech's at one of the larger online stores that I was not happy with my actinics and this was my reason to make the change.
He asked if my Actinic PC bulb flickered slightly. I figured he was going to tell me the bulb was on it's way out, instead he informed me that a "true" PC Actinic bulb will do this, if it does'nt, chances are I had not purchased a real actinic bulb.
I was informed that it would not flicker on and off, but a slight flickering along the length of the bulb, sort of like a veining pattern that you see when a normal fluorescent bulb is dieing out.
I cannot tell you if this is fact or not, but thought I would pass this on to you,