If these are offers or counter-offers you received as a seller, the listing only ends when the buyer completes the payment now.
This encourages buyers to pay quickly, since the item remains listed and available for others to purchase until payment is complete; and it discourages users from making nonperforming offers as a way to take the item off the market until the seller can relist after four days.
If you want buyers to be required to pay within an hour, be sure to check the appropriate box in your Buyer Requirements to make the buyer provide a payment source to place a bid or make an offer.
