I called Panasonic's Plasma Concierge Hotline, 800 973-4390, and here it what I found about this issue;
1. Pixel Orbiter added to 2008 models, moves picture around slightly to reduce risk of inconsistent aging of pixels across screen ( what some call burn-in ) from sidebars, crawlers, fixed station logos, etc on some program material. Panasonic also developed new phosphors that are resistant to image burn-in;
2. The recommend for first 100 hours, minimize / avoid material with above listed type material, and bright games;
3. Preferred mode to use in first 100 hours is "Cinema", but "Standard" also OK ( avoid "Vivid" or "Gaming" mode ).
You can adjust down Brightness, Picture and Sharpness lower to below 50 as some posts have suggested if you want from these modes during first 100 hours).
The rest posted here on this issue by some seems overkill to me based on this. Do what you feel is appropriate.
BTW, rated half life of brightness for this TH-58PZ850U 2008 model is 100,000 hours, up from 2007 model = 60,000 hours ( better than CRT and LCDs, generally 30,000 and 60,000, respectively. )
Also, Should not hum up to 9200 feet above sea level ( up from 2007 model = 8858 ft. ). Life or picture not affected by altitude, just creates hum.