Shane at micro did an experiment with a couple of lights that were tested brand new then retested a year later.
There was a QB in the measurement test. The QB has a sort of lens cover on it which might reflect heat back to the board thus making the diodes warmer than a bare board, in turn deteriorating them quicker.?
View attachment 5294375
I've a couple of boards, Chinese Fotops and R2Ts and a few QBs that are around 5 years old that are still producing the goods. 5 years at 12 on for 365 days a year x 5 is ~ 22,000 hours. About another 5 years left on them! Lol
I can't really tell much difference.
900 umols canopy with a par meter and all is well