i have 2-- HO (T12) cold start 8' fluorescent lights, with some randomly placed, cheap plug in 4' fluorescent.
i noticed the big 8' lights were getting dimmer than the cheap 4' lights.
(talking to wife, she said those big lights are 7-8 years old)
the HO 8' lights were like a movie scene with the heavens opening up, and angels descending, when i first got them !!
but it is dark in the garage now, so i went and bought new tubes for the 8' HO lights and WOW
what a difference
when i went to get the new bulbs, i decided to buy one more 8' HO fixture to replace one of the small 4', but its so bright now i don't know if i need it.
but, i got it now, and you cant have too much light, right?