Thank you for your question.
In South Jersey as you know time is of the essence.
Let's see, your clients have a house to sell and they submitted an offer on a home but they need the proceeds of that one to buy.
Now if the sellers of the house they are buying get another offer from a non contingent buyers your clients will have 48 hours to lift that contingency and go through with the sale non contingent should the sellers enforce that clause.
Now if the deadline on the agreement for closing is getting closer and they still have not found a buyer for their house and the sellers are willing to extend it your just prepare the extension until either party calls it quit.
Hope I answer your question.