I have a Brother HL2240. I installed a new Brother TN450 toner cartridge in July 2015. Now, a year and a half later, the right side of the page prints lighter than the left. I did everything Brother suggested I do...shook cartridge, skid green tab back & forth 15 times, took printer off toner save mode, increased density to darkest #6 setting...problem still exists. You can read the print on the right half of the page, but it is still lighter. Printer reports plenty of drum life and toner left. Does toner go bad after a year and a half? If so, why is the left side perfect? I have used the same 20 lb Staples multi-use paper I always use. Before I buy a new toner cartridge, does anybody have any ideas? Thanks.