It is common that LEDs last 100,000 hours. Considering that 100,000 hours are over 11 years (24 hours a day, 7 days a week), it is very difficult to make real life tests of these products!
The researchers then defined conventional tests to estimate the life of LEDs, based on relatively short cycles. Unlike traditional light sources, the LED does not "burn" but over time it reduces the intensity of the light emitted. Although there is still no industrial standard that defines the life of the LED, the most important manufacturers set the term of life when the LEDs reach 80% of the initial light emission. The average life of a LED is usually shown in the graph consider replacing a LED when its brightness is reduced by 50%. (it is important to specify that the graph was considered a LED with a junction temperature equal to the room temperature and a driving current of 350 mA).
One of the critical factors of the LED is the temperature: the light emission decreases with the increase in temperature. The maximum operating temperature (at the junction point) is normally 100 ° and must not be exceeded: the generated heat is dissipated from a printed circuit according to the sequence: junction, metal body, printed circuit board, heatsink, environment.
The lifespan of LEDs therefore DEPENDS from a correct thermal design of the luminaire. The heat generated by the LED must be disposed in such a way as to ensure the maintenance of the light flow.
Equally important for LED life expectancy is the DRIVER (or power supply): Proper Constant Current power supply guarantees a long lifetime of LEDs.
As mentioned, LEDs, as semiconductors, have a very long life even though some factors contribute to shortening it over time; some of the components that most contribute to the aging of the led are the silicon gelatin used to fill the spaces around the chip. The lens and the gelatin with time are opalescent and tend to yellow by altering the color of the light and consequently decreasing the efficiency of the led.
These phenomena are spurred by continuous overheating, excessive working currents, and numerous power-on / off cycles.
The deterioration times, however, remain very long, on average in the order of 50,000 hours, not even comparable to 1,000 hours of incandescent lamps.