It's odd how Nitemare is the only one (I think) who noticed the input lag increasing after a while.
I've had my fair share of gaming sessions lasting several hours on all 3 of the Samsungs that I purchased, and I haven't noticed input lag increasing on any of them. So either mine aren't doing it, or it's not enough to be noticeable, or I don't have a setting enabled that would be causing it. I'm at a loss, but if it were a widespread issue I would think that more people would be noticing it.
Interested in his comparison of Game/TV mode chroma to PC mode chroma in games on the stock firmware, though. I remember trying to use Game mode before they made it look so much better with firmware 1207, and to me it was not very visually pleasing...PC mode looked significantly better.
I don't think the lag increase with time of use. It increases with how often you switch input to a different source or activate a smart function. It's basically all the junk code being accumulated in the OS if you have instant on set to "On".