What is the useful life of a 30" Cinema Display?
Well, depends on what you mean. I'll write you a novel. I've got one centered between two 27" LED Cinema Displays on my 12c cMP rig. The 30, hands down, is the winner. It's HUGE compared to the grand kids. The matte display is incredible. I use the 30" as my daily reader and check it against everything I do before publishing content. For me, the extra vertical pixels provide the perfect working space in Premiere and After Effects, The other two displays I use for bins and monitor previews. I like the 27 form factor a lot though. Since Apple abandoned traditional input for thunderbolt, I've held a lot of value into the 30 and 27 ACD as it can be plugged into anything with a display port (including thunderbolt). I just recently nabbed a new reburb 27 that popped up in the Apple store thinking it will replace my 30 if that day ever comes...
Back to the 30, I think a lot of it depends on what version you have. I happen to have the refreshed model that had better brightness and contrast. I think the 2004-2006 hardware might be pretty long in the tooth these days. Got mine new in 2007 (god was that an expensive toy) and never looked back. I really wish I could still buy one today. The two grand kids might be a bit sharper, but at times, I despise the glare and reflections. I will run this 30" into the ground. I think the most common problem with the display is they tend to blow power supplies. I wish I could pick up a spare for mine just in case. I've always treated the power supply as best as possible though. I turn the display off when not in use, and keep it's power supply off the carpet and make sure it's not in a strained position. I think if you take care of something well enough it should last a long time. I'm currently hoping my rig will run for many years to come. At work, my cMP was replaced with a nMP with dual thunderbolt displays, and honestly, I would just rather work from home.
The most you have to worry about is power supplies and discoloration as the LCD ages. I have a hardware calibrator and calibrate all 3 displays monthly. The hardware calibrator usually puts my brightness down to almost nothing and I'm glad. If I threw it all the way up, I think I could help usher in world war III. The previous poster mentioned the Dell, I can't speak to that, the design of the ACD to me is great. Everyone's all hyped up about retina displays, and I get it...but I would much rather be sitting in front of a nicely calibrated 30", no mirror, ACD. These things are truly a sight to see. Friends call me crazy, but I really think there is a lot of value in both the old form 30 and 23 displays and classic mac pros. If my house burned down today, I have no idea what I would do to replace these beloved units. If you can get a 30" for around 400 or 500 bucks, buy 3.