During discussion of this meta question, it was noted that our current rules are different from our historical rules. As a result some older challenges would be closed as off topic if posted now. Notable examples are some of the older popularity contests mentioned in that question.
As new users are much more likely to have seen old challenges on main than to have browsed meta, it seems misleading to leave these challenges open, inviting similar challenges. Especially since this wastes the time of people we are hoping will join our community.
This applies to all challenge types, not just popularity contests. How should we deal with historic posts that are no longer good examples of what is on topic?
Should they be closed as off topic? Should they be locked to prevent further answers? Should they be edited with a warning that further challenges of this type are no longer accepted?
Ideally we can settle on a single consistent approach to avoid any further confusion or disappointment for new users.