Plug and play LED will always have problems because they don't have a current-limiting resistor. The biggest problems with LEDs is they get too much power or too much heat. I've been doing some research into LED lighting here is some good info from
http://led.linear1.org/category/led-basics/
http://patmullins.com/ledlightmyths.html :
Long Lasting, Long Life
LEDs have a reputation for long life, but they are also easily abused. Light Emitting Diodes are more fragile than some designers are aware, but electrical or thermal deficiencies in their fixture design will not often cause a sudden failure. Too much current or too much heat for example, could result in a 50,000 hour part lasting only 10,000 hours.
High quality, high output monochromatic LEDs can provide 70% of their original lumen output at 100,000 hours
IF they are not abused. Note that Monochromatic is stipulated because the Phosphor in most white LEDs can degrade faster than the LED junction itself. This can be caused from thermal overload or from excessive ultra-violet exposure. Some manufacturers have overcome these problems, now the integrator must adhere to good science.
