Why LED's life to light attenuation measurement?

LED lamps for general service life is 50000 hours to 100000 hours. With the passage of time, the luminous flux LED lamp long time becomes small and not completely scrapped. This light weight is called "decay", the time available to a LED lamp (working time) with depreciation calculation.
Industry standard to assess the service life of the LED lamp is used as an evaluation point reached 30% when LED light source decay. 100000 hours is not equal to the service life of a lamp. The service life of LED light source is rated to 30% times when the decay of waste. LED light source for more than 10 hours will still work, but the flux will reduce.