When I play too much tetris I start thinking about the blocks all the time and find it maddening. I wonder if these guys can ever stop thinking about the blocks or if it just becomes so hard-wired in their brain that they lose consciousness of it.
There is a well documented thing called the Tetris Effect, where you see the blocks in dreams or when your eyes close. There's been some neuro research on it. When I asked these guys about it, they said they got past it after a while. They all say, yes, I have experienced Tetris Effect stuff, but at some point the brain seems to filter it out. My impression is that these players are spending a lot of their conscious…
There's even a song and music video about it (albeit in german): http://www.youtube.com/watch?v=6lWQGNSqZ8o