I bought my 1st LCD monitor back in 2002; a 19" Planar PX191 that uses a S-PVA panel. I gave it away to a friend two years ago and it still works today. That's 8 years. However, it was an expensive monitor for that time. Even though I bought it sale for around $625 - $650 it was still expensive compared to other 19" monitors using S-PVA panels.
My 26" NEC LCD2690WUXi and 26" Planar PX2611w are relatively young compared to my old Planar PX191. I bought the NEC back in 2007 and the Planar in 2009. Both use IPS panels. I'm hoping they will last at least 5 years.
Additionally, in 2008 I bought the 24" Asus VK246H which is my 1st TN panel monitor. I just wanted to get something cheap to attach to my HTPC to monitor some video encoding processes from time to time. It only gets used maybe at most 4 hours a month nowadays. It actually turned out to be pretty good for gaming so I've recommended it to others who were looking for a gaming monitor.