Here's what the eBay site says:
You cannot retract the bid during the last 12 hours of the listing, unless the seller agrees.
Please contact the seller to request that your bid be canceled. However, it is up to the seller's discretion whether or not to cancel your bid.
I have had bidders retract their bids within the last 5 minutes.
It was quite a while ago and actually I think they had placed their bid within the last 12 hours.Is that in recent history? As I understood it the site will not allow you to retract in the last 12 hours UNLESS you have bid in the last 12 hours