If I am reading the chart right, the 60,000-hour-lifetime stats are actually way too low. At 60,000 hours, the PDP luminance would still be at roughly 300 cd/m2. That compares very favorably with "zero hour" luminance of 400 cd/m2 and "peak luminance" of 420 cd/m2.
It also looks like 3rd-generation PDPs -- what I'd assume are current models -- have licked the rapid-initial-decline in brightness problem. I suspect what used to happen is that something had some very initial early breakdown under the bombardment with UV or whatever wavelength was doing the damage. Some reformulation of the phopshor in the latest generation has "protected" against that breakdown.
An odd side effect is as the chemistry changes in the initial ownership period -- again all due to various kinds of EM emission, plasma gases are chemically inert -- the display actually gets brighter.
Note that the way the curve shown above is built, it has to be from actual-usage testing not unrelated approximations.
Not also that the 37" LCD must be the Sharp. I have one. I hope the CCFLs can be replaced at some time, because they sure as hell ain't going to be all that satisfying.
It is worth noting that data on CCFL (cold cathode fluorescent lamps, the stuff used to make LCD backlights) performance over long periods has not generallly been well studied with respect to peak luminance. Most laptops have never lasted long enough for it to matter.
I'm sure there is lab data at Sharp that refutes the above chart and says, "Hey, our lamps last way, way longer than you claim they do." But I think the important takeaway from the above is not that LCDs have lousy lifetime, but that current plasmas have lifetime that excceed any reasonable expecetations a consumer might place on them -- they are 20+ year displays, as we've been saying.
Now, that said, it's time to get answer on LCD backlight replacement possibilities and cost. It's also time to start getting some lifetime measurements on these things that are backed up by data. There are probably 24 backlights in my display. While the intrinsic cost of each lamp is on the order of $10, I doubt I could buy them for anything less than $50 each -- if at all. I also want to know whether the display should be babied a bit more. If it's really going to be noticeably dimmer after 5,000 hours, I'd try to get it into a bedroom sooner rather than later. It would be fine for many years in that environment as I can't imagine using a bedroom TV much more than 5 hours per week.