Every course on edX.org, including those which are "self-paced" will have an end date. To earn a certificate on the verified track you will need to have a passing score by the end date.
You can see your courses end date under "Important Course Dates" on the right side of the Course tab within the course:
In most courses it will still be possible to view the archived course contents after the end date, however the course staff will no longer provide support in the forum, it will not be possible to earn a certificate and some assignments and other contents may be removed.