If no other student has requested the book, you don't have any overdue loans, and the book permits renewals, you can continue to renew it until the end of the semester. In fact you shouldn't need to take any action; most books will be automatically renewed three days before their due date. All items are due no later than the end of the semester.

If someone does put in a request for the item, you will need to return it by its due date. You can always sign in to your library account to see the due dates for your checked-out items.