Unfortunately a seller can respond or not as they please. Your offer should have an expiration date and time, offers should not be open ended. My take away is that the seller and/or their agent are playing games trying to see if they can't get additional offers. Whether you decide to play along with them is up to you. If you wish you could have your agent resubmit your offer with the caveat that the seller has 24 hours to accept it or counter, after which you are pulling your offer and will no longer consider the property. Ultimately it's up to you to decide how much jerking around you're willing to accept from the Seller and how badly you want this particular house. My own experiences (25 years worth as a top producing broker) is that when one side or another starts off playing games, it's an indication you're going to be working with real jerks.