I have not played games for hours on end, however, my wife did play with some of the simple games that came with the TV firmware. I have been looking for any image retention with TV station logos. In our case. there has been no image retention that I can see. My picture settings are similar to the THX settings.
Some reviews were suggesting that IR would be a problem and I suppose if someone play the same game for two hours in vivid mode that there would be some IR, but I do not do this.