When to change bulbs?

[fishfood]

What is the lifespan for VHO bulbs? I've had mine for 10 months now i think and was wondering if they should have been changed already?

 

[dirtybilge]

It depends on your ballist inf its an Icecap they claim there good for 12 months if its not Most VHO's die after 6-8 months.