The lifespan of a LED (chip) is defined by the extrapolated time taken for light output to degrade by 30% (L70). It is common for LEDs to last between 15,000 hours all the way up to 90,000+ hours. However only a handful of manufacturers actually have products which have been tested longer than 50,000 hours.
The issue with the quoted lifespan of the LED is that it is not a whole of product lifespan. Our general guidelines are to follow the warranty period as an indication of the product lifetime. For example, if the product states 36,000 hours, then you would expect the product to work continuously for 4 or more years and be backed with a 4 or more year warranty.
The lifespan of a LED is vastly longer than that of incandescent, fluorescent or HID. A light emitting diode never really burns out, which is why the LED lifespan specification, to be meaningful, is quoted as lumen depreciation.