The problem with major torture is a balance between enough pain or discomfort to exact the correct response, without applying so much pain that the victim loses consciousness or becomes immune to the pain.
For instance, sandblasting someone would suck for them, but after you did that, they wouldnt feel anything further because they more than likely would be dead before you finished.
The body can only deal with so much before it shuts down. The balance is finding the point where the victim passes out from the pain or discomfort and then only taking it to that point. That way, the torture can both be long and brutal.
CK