I take it you are asking the life span of the bulb. I've never had PC but VHO is stated between 6 Months and 1 Year. I've heard with the Icecap ballast that VHOs are still good at 1 Year. I've had VHOs on my Icecap 10 Months now. No algea and still looks bright. I'm waiting to change them at a year if all goes well till then. They are URI bulbs.