I know I've seen this discussed before . . .

Ah. http://dw-suggestions.dreamwidth.org/605967.html -- would have been a journal-wide setting a la use case #2, deferred.

I still would like to know this as a reader ("This post is scheduled to become non-public / to become public / to have its access requirements change on date" -- not sure the best way to handle changes involving filters), which is my with-changes.