Its never the actual LED, but it is always the controller, or power supply, or some other component. That is why you see LED light bulb manufacturers talking about 35 year life span but only warranty for 1 to 5 years. They know they aren't going to go for 35.Assuming they are LEDs, that won’t happen for a long time.
But in the case of Spaceship Earth, I am guessing they are expecting a fairly good life span, and in the vent of a failure, it is going to be a case of getting out the boom lift and repeating the install process. With the right gear it isn't that hard,