The newer LED TV's don't last as long as the old CRT tube TV's but you should get at least 5 years out of an LED TV but for the cheaper ones you might only get a few years out of it.
I had an old CRT tube TV that was 20 years old and still working when I got rid of it for a new LED TV but I've so far haven't made it past 5 years on an LED TV before the stop working or the picture starts dimming.
My mom bought a cheaper LED TV at Walmart and she got 2 years out of it before she had to replace it but she watches a lot more TV than I do.
The more the TV is on and the more TV you watch the less time the LED TV will last.
I've got an LCD computer though that is 12 years old and although it's dimming a bit it still functions and I use it just to keep the Google Analytics page loaded on my computer to watch the visitors to my blog.
If it quit I would be okay with it as I've had it for 12 years.
I've also heard of some people who say they still have their LED TV working that is 8 to 10 years old but if I got 10 years out of an LED TV I'd be okay with that as well.
10 years is a long time and by then I'd be ready to have a new TV delivered to my house anyway.