We know that CCFL will dim over time. https://www.google.com/search?q=LN46D630&ie=utf-8&oe=utf-8#q=LN46D630+ccfl shows this model has them. Get estimates for their replacements.
I purchased this 46 inch hd Samsung in June of 2012 so it is out of warranty. The picture appears to be slowly losing it's brightness. For example, any shadows on a program appear almost completely dark now. I've tried resetting and increasing brightness with no success. Please help