I wouldn't even wait a week, honestly...I generally give it 24-48 hrs, unless I know that the person has not visited the site. (Occasionally, I will withdraw sooner, if I know that I won't be available to respond with payment in a timely manner; but it is rare...and, if I REALLY want the knife, I might give it extra time; but that is even more rare.) Also, I only make offers via PM or email; so it is between me and the seller. If you posted in the thread; I would edit the post to state that the offer is withdrawn.