I've had a Panasonic TH-42PW4BX for a month now. I've only had time to watch a few DVD's on it, but I have noticed the factory presets for the contrast setting seems excessively bright - around +25. I've done some research, and some experts seem to suggest dropping the level to around -20 (reducing burn-in risk), which I must admit seems too dim. Does anyone have any "official" guidelines on a sensible level? I could probably get used to -20. Many thanks in advance for any thoughts.