Hi ATI NA, Just wondering how often I have to change ballasts if my lamps working 12hours per day? I have T5 ATI powermodule. After 2-5years will be good or I have to change them only if the ballast doesn't work? How I can check if the ballast is not reduce the power of the light intensity? What brands of ballast you will recommend for 39w and 54w tubes? Thank you.