Once the bulbs start flickering or stop working their brightness is greatly diminished. It's best just to replace them every 18 months - 24 months. You'll notice the difference when you put the new bulbs in.With Advance ballasts, which are high quality programmed start ballasts that are easy on the bulbs and that drive the bulbs at HO levels, not the very hot VHO levels of Icecap ballasts, do you think I need a few 3 in. fans in the back of my canopy?
With these bulbs, do you just replace your bulbs when your bulbs start flickering or stop working?
What I know on the subject is mostly just experience. I have a 4 x 54 watt Tek fixture and another 4 x 39 watt fixture with DIY IceCap SLR reflectors and T5HO ballasts from ballastwise.com. I'm not sure which ballast is in the Tek fixture.It sounds like you guys both know more than I do on the subject - I am interested to know why my T5's don't last as long as yours.
It is fairly common consensus in our local group that T5's go for about 9 months. They don't burn out or flicker, it is just that their light output is significantly diminished at that point. Which ballasts are used in the Tek fixtures? Mine run very cool with no fans... Perhaps changing the ballasts will extend the effective life of my bulbs? Getting twice the mileage on my bulbs would save quite a bit of money over a few years.
Hope I am not dragging this off topic too far...