Yeah right I had no idea humidity would have a negative effect on the diodes. I try to get my humidity as high as possible in veg and am often in the high 70s with lights on and into the 90s with lights off. Water dripping down the walls stuff.Humidity and burning sulfur also does a nice number on them, we seen more boards grow dodgy in our veg space. Sealed boards should be better as long as the temps are similar.
Thermal cycling also seems to affect the actual pcb - my mate did a bare board light on very low watts and had a few boards fail completely; not burnt diodes but just board stopped working.
I'm now even more impressed with the longevity of these lights!!
Current pic!