I am considering purchasing a used Plasma on eBay. According to Wikipedia:
The lifetime of the latest generation of plasma displays is estimated at 100,000 hours (11 years) of actual display time, or 27 years at 10 hours per day. This is the estimated time over which maximum picture brightness degrades to half the original value.
I am guessing there's no way to know if the owner left it on 24 hours a day forever?
And what happens after 27 years, the display simply gets half bright, but still probably usable with extra lighting?