Be sure to get up every couple of hours to do some stretching for about ten minutes to keep the blood circulating properly in your body and to try to prevent blood clots!! No joke on this. The body doesn't do well when it's immobile for long period of time!
I actually just got a blood clot and got very ill. So i'll be getting up every hour to stretch and walk for a minute. Before that I was gaming for 10 - 12 hours straight sometimes.