The main reason for the failure lies with the dissipation of heat generated by the LEDs. MR16 LED spotlights are smaller than most LED lamps, thus thermal management systems play an even more critical role in achieving the lumen output and efficiency of the LEDs.
The article also mentioned that quality of light and life expectancy of the LED lightsource decreases dramatically if heat is not dissipated properly.
As consumers, the solution to minimise getting a lousy LED spotlight is to buy from a reliable supplier with good track records. For an exact looking product, the price range can be from as low as $6.00 to as high as $15.00. In my opinion, getting an MR16 LED spotlight at a price of $10 - $12 gives a much greater assurance going forward. This will maximise your returns on investment too.
Source of below article - http://ledsmagazine.com/magazine&id=17914, February 2013 Edition, page 7 of 80