In principle, a payment link does not have a 'shelf life' and remains valid until it is clicked. As soon as a customer clicks on the link, a payment is created. If the payment is subsequently not made, it expires after 15 minutes.
It is, however, possible to make multiple payments with the same payment link. This also allows you to send the link to multiple customers. Please do take note that in this case it can be difficult to keep these payments separate. You will have to do this based on the account name that appears alongside the payment.