I agree, I think there are people out there who think just because the bulb is shining and not burned out that it is still good. This was something I myself learned on the forum here.
The bad thing is you need a uv meter to tell if your bulbs are good. I have some a year old that still put out good uv. one of the resons i use 10.0 bulbs even when they get a little older they still put out like a new 5.0.