There has been some discussion on this topic, and I would like to hear ideas from the floor (hehe). Some people are saying that waiting 7 days for a player to accept a challenge, and then waiting 7 more to play the match. Yes that can be very slow. Apparently people here are action junkies

because they are also complaining that when they have a challenge pending, they cannot be challenged from below. Heres a solution:
Challenges must be accepted within 3 days (72 hours), and matches must be played within 7 days.
I must insist on this length of time to complete the match, because it may take players that long to find a common time. I will use myself as an example, I work a week on week off schedule and have very littel time to play during my on week, so for me to complete a match within that week would be difficult.
Accepting the match should be a relatively short period of time. IF you know you wil lbe gone for longer than that, just request to be placed ia for a period. Any shorter though is impractical, again for people like myself with wacky schedules.
While you have a challenge that you issued pending, you can be challenged from ranks below. Both challenges are valid, but upon completion of one, the other must still be valid after the new rankings are determined.
Meaning if winning or losing one of the challenges pushes outside the 3 player boundary, the second challenge is then voided.