Black Bars. What's the deal?


I have a 55 inch Mitsubishi wide screen rear projection t.v. I own over 100 DVD movies and most of them are in 2.35 aspect ratio. When I play them I have top and bottom black bars on the screen. When I play the DVD's with 1.85 aspect ratio it fills the entire screen. In my t.v. owners manual it has a page warning you not to leave stationary or letterbox images on screen for an extended period of time and that uneven picture tube aging is not covered by my warranty. Example of these are letterbox top and bottom black bars, sidebar images, stock-market report bars, shopping channel logos & pricing displays, video game patterns and scoreboards, bright station logos and on-line internet web sites. I have been using my zoom function on my DVD player to fill the entire screen when using a 2.35 aspect ratio DVD. A fellow at my local audio video store told me that the black bars at the top and bottom can not burn a lasting image on my screen and when I use my zoom functiion to fill the screen it degrades the picture quality of the DVD. My question is: Will the black bars ruin my t.v or not? Any comments will be greatly appreciated. Thanks in advance.
jondon
I cannot speak for the Mitsubishi brand, my experience is with a Pioneer rear projection system.

Mine has seen at least 300 hours a year of letter box program, with nine years of service. It also sees full screen programming via DSS signal the rest of the time.

With about three thousand hours of letter box, there is no effect from the letter box bars. I am certain my entire image is way down from when new, but that is another issue in itself.
If I am not mistaken the projection type units should not be affectied by this problem? It is the same idea as the screen saver on a computer CRT not letting an image burn itself onto the screen by keeping the image from being static for very long. The phosphores in the CRT itself are what I understood would be effected.Again if I am not mistaken,the projection type units work under a somewhat different principal. I think if you ran letter box images 24 hrs a day for along time it may do what they are warning against on a direct view(cathode ray tube) set. We need a TV "tube" guru to tune in!
Yes/burn in indeed.--From webtv.Took me a long time to notice. I now use what Poneer calls "Full Cinema"

This is vertical. The horizontal doesn't work the same way--Not this constant white/black.If one were to put a bright (top 1/2 of the picture) on pause--long enough;you'd get them there cosmic burn-in-blues--too.This will occur in a non calibrated set even faster.
My Tosh 56H80 does nothing but DVD and LD. No cable, no DSS and no OTA. The set was V.E calibrated upon first turn on with emphasis on corect white level and black level. With only about 300 hrs on the set I noticed very,very faint shadows of the black bars from 235:1 movies. These could only be seen during a totaly black scene(like a fade to black)on a 185:1 movie. I started using one of the set's "theater wide" settings, which fills the screen but crops the sides, for re- watching old favorites. First time viewings and/or critical watching are allways done OAR! Now after filling the screen more often, these shadows can only be seen with the room totaly dark and grainy or noisy 185:1 DVD(older movie like "Dogs of War")is in and an all black scene is displayed. I hope I can continue to reverse the process of the burn in as it looks like I am making progress.
Not that it really matters, but I thought it is the illuminated center part of the screen that wears with use. The black bars are not used and thus stay essentially as new.