That's right, but that's expected only when the pixels are activated for a prolonged period of time, e.g. when a certain screen image is displayed on the screen for several hours without moving it.
All products get worn down, so damage is expected after a number of years - it's just a question of how many.
Yes, it is replaceable. But if the device breaks down after a period of time such that the device is already obsolete, then it would be difficult to find replacement parts by then.