Frankly speaking, there is no way. I was surprised when I kept looking through all the settings to find nothing on how to disable the screen time out in a Samsung Galaxy S2 phone. The screen time out only has options for 10 minutes at the most.
I hate screen time outs, hence the need to disable it. Keep Screen, an Android app is the solution for this. While it does not disable screen time outs in general, it will keep your phone from timing out on certain applications that you set not to time out.
The app is free. Last I saw, it said “for now” so better hope when you go to the Android Market and look for it, it is still free.