The life for led lights
Why is the life span of an LED measured as lumen depreciatio
The life span of an LED is vastly longer than that of incandescent, fluorescent or HID lamp sources, generally lasting 50,000 hours or longer. Although the LED never really burns out, product life span is measured by lumen depreciation.
The Illuminating Engineering Society's (IES) current standard for calculating the life of an LED as the point at which the LED reaches 30 percent lumen depreciation.
Remember, a 100,000-hour rating is not equivalent to lamp life rating. LED life is rated where it has reached 30 percent lumen depreciation. At 100,000 hours an LED would still be operating, but at a decreased lumen output.