At SitePoint, we do not believe in sniping. Just like in real-world auctions, we give everyone involved in an auction the opportunity to respond to a bid before the auction ends.
For this reason, any bid made in the final 4 hours of an auction will postpone the end time of the auction to 4 hours after the bid was placed.
Buy It Now bids are of course exempt from this rule, since they trigger the immediate end of the auction.