You do not need to take all of the courses in a program at once. You can take the courses in a MicroMasters™, Professional Certificate, or XSeries program individually when they are offered. All courses which are part of a program are expected to repeat several times a year.
Most courses only show the currently available session, but some courses in programs show the available sessions over the next year or so, so that you can choose the session dates that work best for you. For more information, see How do I complete a course when multiple sessions are available?