prophet: Whether the system encourages or discourages longer matches is not a simple question. Under the ELO formula, when players are of roughly equal rating, then a longer match will result in a greater rating adjustment regardless of who wins. However, where there is a significant ratings difference, then after a certain point a longer match can actually result in a smaller adjustment. This is because the ELO formula takes into account the probability of either player winning the match. As the match gets longer, the probability that the higher-rated player will win increases, and the ratings effect of a win by the higher-rated player gets smaller. Of course, if the lower-rated player wins, then the ratings adjustment is always larger in a longer match.

Therefore -- the current system, which does not take into account match length, actually can be seen as encouraging high rated players to play long matches against low rated players. This is because the high rated player is more likely to win a long match than a short one, and yet the ratings adjustment will be the same for the long match as for the short one.

If players are of roughly equal strength, then the failure to take match length into account should be a neutral factor. At the start of the match each player's expected outcome is zero, i.e., there is an equal likelihood of +x or -x, since it is not known who is going to win and both have the same chance. It doesn't really matter what value is assigned to x.

If anyone is discouraged, it should be the low-rated player, who will not be properly rewarded if he does manage to win a long match against a high-rated player.

If there are players who grumble that it's too much trouble to play a long match for a relatively small ratings adjustment, my response to them is that it's more fun and a greater test of skill to play a long match. In addition, if your self-esteem depends upon achieving a high rating on this server, you really need to reconsider your goals.