I would think LEDS would outlast the panel they are backlighting in many cases. I have items with LEDS that I made before 1970, and they still work. One of them was a power supply I made in 1968 or so, with a big red LED power indicator, that has probably been on for over 30 years of that time period. It looks the same as it always has, it's not really ever been that bright, to be honest about it.
I have had a couple of CCFL monitors that have faded down over the years, but none that couldn't be "fixed" by simply turning the brightness up. Nothing has ever dimmed like one of my CRT monitors did, an NEC that got so dim it took an hour before it was tolerable in a lighted room, and even then, just barely. It was really expensive though, so I lived with it way longer than I should have.