From what I've seen date, you can archive pretty much anything and in any state where the option is available...That said, for su, it’s more about what data I can get out of the system after a record is archived. We found that survey, exam, and most learning objects are no longer reportable after they are archived so we only use it for some course, not all. I would recommend you run some tests to make sure that once a course with an assignment is archived, you can still see whatever you need to see in your reports or under the archived data, otherwise don't do it. Archiving cannot be reversed or edited at this time