Is burn-in related to the dimming of a plasma display as it gets older?
Yes. When a plasma display burns in, certain pixels dim while others remain bright. If you fully saturate the left half of a plasma screen (i.e. make it bright white) for an hour and leave the other half black, the left half will appear to be dimmer. Blue pixels dim more quickly than green or red pixels. Thus, with normal use, after a few years, the blue pixels will dim somewhat more, and the screen will appear to have “yellowed”.