If you use your LED computer monitor for 8 hours per day the LED computer monitor should easily last for 8 to 10 years and sometimes longer.
Usually you'll be ready to replace the computer itself before your LED computer monitor dies on you.
I have a 13 year old LCD computer monitor made by Dell that works great although it's just a smaller monitor but it works okay for some things I need it for.
So you should get at least 8 to 10 years out of a new LED computer monitor before it dies.
My current LED computer monitor is only a year old so we'll have to see how long it will last but I expect it to last quite awhile.