That is interesting. But note that he was starting with a unit of 1 second of torture. 1 second of waterboarding is not 1/30th as distressing as 30 seconds of waterboarding. And 1 second of Chinese water torture, or the ice room, or simply isolation, is less disutility than dust speck. Actually, the particular case of isolation is one where the 50th year probably is worse than the first year, assuming the victim has not already gone completely bonkers by that point.