tippyc:A proper ratings system would make adjustments which reflect the probability of the outcome.  This in turn is a function of the relative strengths of the players and the length of the match.  The longer the match, the greater the probability that the stronger player will win.  Therefore, if the stronger player does win, the change in ratings should decrease with the length of the match.  If the weaker (i.e. lower-rated) player wins, then the change in ratings should increase with the length of the match.