Monitors/Lifetime of LED Monitors
I have 3 LED monitors and use them 12-14 hours a day due to my job. How long can I expect them to last?
Honestly it's somewhat tough to say - MTBF for CFL-based LCD monitors usually ranges around 30,000 hours (that's like ~3.5 years of 24x7 operation, or around 7 years of your usage), and LED-based LCD monitors in principle should last longer (non-backlit devices can last for decades if they're well cared for, for example). However, MTBF is a theoretical number and doesn't account for the actual "aging" of the device, for example capacitors aging and failing, or if the device sits in sunlight often, that can have a negative effect.
I think it would be fair to expect 4-5 calendar years assuming nothing catastrophic happens (like a liquid spill or power surge), but even that may be an optimistic goal given your fairly heavy usage. I'd also certainly agree with going with LED-based displays for this kind of heavy usage, as opposed to CFL-based or non-LCD tech (e.g. Plasmas). My advice would be to look for displays with 3-5 year warranties (Dell and Samsung generally offer this on their nicer monitors, for example), and depending on how mission critical these displays' role is, replace them when that warranty expires. That will at least ensure that whatever displays you're using are "covered" - if they fail while under warranty they should be repaired or replaced under warranty.