Calling All Panny Owners

This whole Panasonic plasma black-level thing really bugs me, and I'm not alone. Shoppers are shying away from Panny plasmas because they just don't know if the black level will increase significantly after months or years of use, and frankly, neither do I. In an effort to learn as much as possible about the phenomenon, I turn to you, our readers, for help. To anyone who owns a 2008 or 2009 Panasonic plasma, I pose the following question:

Have you noticed any increase in overall black level during the time you've owned the TV?

I'm not talking about objective measurements here. After all, most owners do not have an expensive light meter, and even if they do, they probably don't make a habit of measuring the black level periodically over time. (AVS Forum members are a notable exception.)

What I'm really asking for is your subjective impression about the black level over time. When you watch a sci-fi movie with scenes in outer space, does the black of space look lighter than it did when you first got the TV? Have letterbox bars become more noticeable over time? Has the picture lost some of its "pop"? A few readers have posted comments to this effect in my previous blog, but I would like to hear from as many as possible here.

I'm assuming that you've left the brightness control alone during most of the set's life—hopefully, you set that control correctly when you first got the TV. If you haven't fiddled with it much since then, any increase in black level must be due to something internal—presumably, the increase in drive voltage that Panasonic admits is part of its plasmas' normal aging process.

Of course, if you happen to have measured the black level over time, I'd be very interested in seeing those results, at least as a relative indicator. Absolute numbers are difficult to trust without knowing the particulars of the instrumentation and environment in which the measurements were taken, but they can provide a relative basis for identifying a general trend.

This problem is particularly pernicious because it manifests itself only over an extended period of time, so reviewers like me don't have the opportunity to observe it directly. Only long-time owners can do that, which is why I'm turning to those who have lived with a Panasonic plasma for a while to help all of us understand the extent of the problem in the real world. Please post your response here, and thanks in advance for your participation!