As long as we're on the subject of CRT displays and their longevity, permit me to rant a little and cross-over some experience from one of my OTHER hobbies, classic video games. It seems to me that video games and CRT-based panelviews have much in common, as they both are left running for days on end in a hot, poorly-ventilated enclosure.
The prevailing wisdom with game monitors is that the CRT itself, although they CAN and sometines DO fail, is a very high-reliability component and usually is NOT the cause of a monitor failure. Heck even when they do, they can often be "rejuvinated" to get a few more years of life out of them. On the contrary, the most common items to fail in a monitor are the electrolytic caps (especially the high-voltage ones), the horizontal output transistor (HOT), and the flyback transformer. Furthermore, bad capacitors can LEAD to premature failure of the HOT, flyback, and other components.
So why am I even mentioning this!? Because if the capacitors are considered a regular maintenance item and are replaced BEFORE they fail, there's no reason why a monitor like this can't live 10, 20, 30 years or more. I have 30-year-old video games with the original monitors to back this claim up. Oh and by the way, the caps are usually VERY CHEAP and are pretty easy (for someone with basic soldering skills) to replace.
For those that want to read more..
http://www.gamearchive.com/Video_Games/FAQs/capkit/http://www.flippers.com/esrkttxt.html