Czuch:  Using the FIBS formula as an example, because it is widely accepted, there are two variables -- match length and the difference between player ratings.  Between players of equal strength, the longer the match, the greater the point adjustment.  Where there is a difference between player ratings, the positive adjustment from a win is greater for the lower-rated player than for the higher-rated player.  Conversely, the higher-rated player suffers a greater negative adjustment if he loses than the lower-rated player would.

Longer matches produce smaller point adjustments if the higher rated player wins, but larger adjustments if the lower-rated player wins.