Dual Displays

I have a dual display set up with two different sized monitors-- a Viewsonic VP201mb (20"- 1600x 1200) which is almost 6 years old and a Sony SDM-HS95P (19" - 1280 x 1024) which is 3 years old. Im going to replace the Viewsonic with another one, the VP950B (19" - 1280 x 1024), which has some nice reviews. So now I'll have two 19" monitors, instead of one 20" one and one 19" one. Should I look into replacing the Sony too? Its three years old and uses an MVA panel. I cant find an MTBF on it-- do you think it should last for many more years to come? Does MVA panel technology last longer than normal LCDs? I might get another VP950B to replace it with, but I like having two different brand monitors. I would appreciate it if you could find some info to let me know what the MTBF on the sony panel is and how many more years the backlight should be good for if I use it 6-8hrs daily. Thanks!

BTW, here is a review you guys did on it:

http://www.tomshardware.com/reviews/19,1164-17.html

It doesnt say what the MTBF is though. If I do keep the Sony, Id use it for emailing and office work and use the Viewsonic for photography, gaming and watching movies.