G'day CAG - There is a whole section on Bids in the FAQ under Auction Rules HERE Please anyone starting an auction have a look at it to sort out the approval problems.
Short answer for you CAG is in the second line of the Accepting and Rejecting Bids section where it says:
"Bids not accepted or rejected within 72 hours will automatically be rejected on behalf of the auction holder by the system."
Hope this is of some help.
Cheers - Neil