1) A game challenge will automatically expire after a period of 14 days.
2) A player may specify an earlier expiration date. This date must be at least 3 days from the date you issued the challenge and must be included in the comments section of the challenge form.
3) In a future site upgrade a player will be able to go to the site and manually cancel a game challenge at any time. This will supercede #2 above when it is functional.