You likely have IR (image retention) not burn-in, and IR does fade over time, it can take a few days in severe cases. True burn-in can take over a thousand hours, even thousands, such as with an on all the time display in a mall. ALL plasmas have less 'burn in' potential than a CRT. Check your settings menu for a band scroll option that helps erase IR, and an image shift feature that automatically shifts still features a few pixels after 10 minutes.