When we talking about lifespan of LED, it refers to L70 which is when the lumen maintenance is 70% of the original level.

It is not convenient to test a LED lamp continuously for 50000 hours. So generally the lab will using accelerated aging test method to get the lumen depreciation situation after 6000 hours or 10000 hours , together with Decay curve fitting, to evaluate lifespan of LED. Currently there are two main standards of testing lumens depreciation, they are LM79 and TM-21. When the test reports meet standards of 50000 hours requirement, we can state the life span of the LED lamp reach 50000 hours.