There's two things that make LEDs fade. The first is the use of low grade phosphors. White LEDs are just blue or UV LEDs with a phosphor over them, the phosphor works the same as it does in a fluoro tube, emitting white light when excited by the blue or UV.
The other problem is heat. Many downlights run way too hot, either from poor bulb design or from fittings that provide inadequate ventilation. This causes the phosphor to degrade faster. With LEDs, the cooler they run, the better.
However, the problem of heat degradation is much worse in many low cost LEDs and hence LED bulbs than it is in higher grade brand name LEDs like Cree, Osram etc. Indeed, some manufacturers, Cree being one of them, are rating their lighting grade LEDs at 85 degrees instead of the more common 25 degrees, and lifespan is often rated at 50 or 70 thousand hours at those temps.
So, if you want LED bulbs to last, buy ones with Cree or similar higher grade LEDs, or make sure you bulbs are running as cool as possible.
Unfortunately, LEDs, being more complex than other forms of lighting, are out of the knowledge range of most people and so you will hear a lot of "LEDs fade too quickly" or "LEDs don't last" or other similar incorrect statements where people will tar all devices with the same brush simply because they bought the wrong devices for their situation because they don't understand the technology...
Posted Thursday 12 Apr 2012 @ 8:33:53 am from IP
#