Hrqls: I don't believe that's the case. There's one formula for the first 25 matches and another for match 26 onwards. Thus at 26, 100 or 10,000 it should make no difference. Achieving stability is a different issue. 25 matches in a luck-based game will often be insufficient to bring a player to their "true" rating but with the current formula that's not accounted for, given that it assumes that there's no luck. The proper Backgammon formula has a diminishing "bonus" factor which lasts until the 399th experience point.
But that's only my understanding from having read (over-complicated) explanations of the Chess formula and from a limited set of observations. The code actually in use at BrainKing is a mystery. Do you have any further data about the points awarded to matched players at different experience levels?