Its a common specification for household devices such as lightbulbs. However, I can't figure out how you'd truly evaluate/prove such a claim without running the device for the specified amount of time.
Consider a lightbulb that is said to have a lifetime of 9000 hours. If I were to test this, the only way I can think of truly measuring this is to let the lightbulb run for 9000 hours, which is approximately a year!
If a year is not long enough, consider certain LED bulbs rated at 50,000 hours!
Clearly its not feasible to run a test for this long. So I guess I'm asking; on what basis are these claims made?
Perhaps one way to test it is to stress the component at higher than normal operating conditions, so that it burns out faster, and then somehow create a prediction based on measurements. Or perhaps run the component for some (short) time and measure the deterioration/ageing and use that to create a prediction.