If you could take all the pain and discomfort you will ever feel in your life, and compress it into a 12-hour interval, so you really feel ALL of it right then, and then after the 12 hours are up you have no ill effects - would you do it? I certainly would. In fact, I would probably make the trade even if it were 2 or 3 times longer-lasting and of the same intensity. But something doesn't make sense now... am I saying I would gladly double or triple the pain I feel over my whole life?

The upshot is that there are some very nonlinear phenomena involved with calculating amounts of suffering, as Psy-Kosh and others have pointed out. You may indeed move along one coordinate in "suffering-space" by 3^^^3 units, but it isn't just absolute magnitude that's relevant. That is, you cannot recapitulate the "effect" of fifty years of torturing with isolated dust specks. As the responses here make clear, we do not simply map magnitudes in suffering space to moral relevance, but instead we consider the actual locations and contours. (Compare: you decide to go for a 10-mile hike. But your enjoyment of the hike depends more on where you go, than the distance traveled.)