Discussing Life Expectancy of LED Fixtures
I'd like to throw this out here for discussion sake...
LEDs have a lifespan rating of several tens of thousands of hours... But will the phosphors that make them emit white light actually last that long?
The reason I ask this is that I've followed very closely the performance of two commercial LED fixtures (one of the best brands at the time of purchase) over reef tanks for the last 24 months. Besides the headache of replacing drivers and LEDs here and there, the overall quality and intensity of the light has greatly reduced over the course of the first year and is below acceptable levels in my opinion over the second year. Now I'm not 100% sure what LEDs were used in these fixtures but I'm guessing they are phosphor coated InGan/AlInGap LEDs just like Philips/Luxeon/Cree uses. I think it's safe to assume we're all using phosphor coated LEDs. My gut tells me that these phosphors, which are practically identical to those used in fluorescent bulbs, may have degraded over time just as they do in fluorescent tubes.
Can people that have been running LED fixtures for over a year chime in and let us know if things look the same today as they did a year or two ago? I'm a big fan of LEDs but when I hear life expectancy claims that go into the 10's of years I start to wonder if the phosphors used will last as long as the diodes themselves.