My 4 year old Viewsonic is going strong still on my daughter's computer and my new Viewsonic is 18 months old, no problem.
I have 3 Dell refurb'd sony's that are all doing well over the past year as well.
My 8 year old Daytek worked fine and was sold off.
I shop at a recycling place that has literally pallets of old monitors from businesses, all for sale and working, most over 5 years old.