When I bought this 25inch monitor 2 years ago I gave the previous 19inch one to my stepson as there wasnt room for it on the machine downstairs.
He leaves it on 23/7 and it would now be just over 4 years old.
Downstairs is the 17inch one I had before the 19 
That stays on 24/7 also. I originally bought that one to use with a laptop. Its 8 or 9 years old now.
They are all LCD screens.
The laptop, also 9 years old (still has the "new for windows 98" sticker on it ) has a plasma screen. No problems with that either.
() 