Typically, the important parts of a light bulb, such as the filament, weaken over time, which causes the bulb to burn out,But LEDs donot burn out the same way that other bulbs do, instead ,the amount of light they produce decreases gradually in what is called "lumen depreciation".The lifetime of an LED bulb is based on how long it takes for the lumen depreciation.The lifetime of an LED bulb is based on how long it takes for the lumen output of the bulb to decrease to 30%, so it will likely last longer than the average rated lifetime hour listed on the box if you donot mind or donot notice the decreased illumination.

Certain cheaper LED bulbs will only last about 5000 hours , which is still 4000 -3000 hours longer than the average rated lifespan of an incandescent, but many branded bulbs are rated for over 25000 hours.