I have done some testing on some PC tubes. They are mainly Coralife tubes. As an example the 96W lost half of its output in LUX in six months. Today I have tested some 65W 50/50 tubes by Coralife. The two I tested were about one year old. They were both down to 2000 LUX, so virtually useless. I also tested a GE 9325W tube, which was also old. It tested at 4000Lux, so it was quite a bit better. I also tested a 24" Helios T5 tube which was only a couple of months old. It came out at 1200LUX, which made it not worth considering as a primary light source. Although this testing was not exact, it still shows a trend.
