Protecting Articles

  Mark as Protected (Ctrl+L) (or Right Click menu in the Thread Pane)
  A protected article will not be purged and can not be deleted until it is marked "deletable"
If the body is not stored locally when you use this command, Gravity will offer to tag the article(s) for body retrieval. You will have to retrieve tagged articles after tagging to fetch the actual article bodies.

(You do not have to fetch the article body to protect it. However, the server may eventually expire the article and the body will not be available)
If you use this method to archive important articles, it is strongly recommended that you save frequent backups.