After the course is over, at some point, the course is "archived". The only impact of archival is that student work area is reclaimed.
As a teacher or an org admin you can always log into Vocareum and access your assignment content which includes all the scripts, starter code, etc. If you create a new course, you can copy assignments from your prior course.
Students can access their course based on the "Access End Date" in course setting. That date can be set by teacher to any time in the future. For example, if this date is when year from the course end date, then students can log into the platform and download any of their submissions.
Submission data is always stored on the Vocareum and it can be either anonymized or deleted upon explicit request by the teacher. After a period of one year, it might be moved to a cheaper storage and might require a few hours to be retrieved.
There is currently only one option for bulk download of submissions. You can go to Dashboard=>Export=>Submitted assignments to get a zip file of all student submissions for that part. That option is always available to the teacher regardless of when the course ended.