It is called the CYA tactic. Most manufactures do this to keep them from replacing tv's. You shouldn't worry about burn in as much, but it can happen.
Everything I read about LCD projection TV's before I bought one said that burn in was not a problem. But the manual of my Hitachi recommends to watch 4x3 standard on this widescreen only 15 % of the time to avoid what sounds like burn in. Are they just being careful, or is this a real problem.

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