AbigailII: N games per year? I'm not sure where that idea came from. Are you referring back to anything I should know about? Either way I agree; it's not useful to impose any such condition.

As for restricting the influence of a pair's large number of games? Horrors, that's the last thing I'd want (if these are legitimate games). Any of the various playing patterns: two people playing a lot against each other, a group playing a lot between themselves, high-level players only playing other high-level players, lower ratings only playing lower ratings, etc - these all do their bit to make the flat lake of perfect ratings/rankings into a somewhat choppy sea. Removing the cheats who cause waves is a good thing but to control any of the other winds and currents .. is it necessary?

But if it is, I reckon the only fair way to ensure the accuracy of all BKRs is to force every player to play every other player in the same number of games within a given time frame. To ensure that last condition, slow players would have their moves made for them by an artificial intelligence whose playing level exactly matches the players style and BKR.