Just to formally document the exact policies we have in place to remove old abandoned / dead questions, the Community user will delete questions in the following circumstances:
If the question is more than 30
days old, and ...
- has −1 or lower score
- has no answers
- is not locked
...or...
- it was closed and migrated to a different site
... it will be automatically deleted.
If the question is more than 365
days old, and ...
- has a score of 0 or a score of 1 with a deleted owner
- has no answers
- is not locked
- has a viewcount <= the age of the question in days times 1.5
- has 1 or 0 comments
... it will be automatically deleted.
These checks are run every week across all sites.
If the question was closed more than 9
days ago, and ...
- not closed as a duplicate
- has a score of 0 or less
- is not locked
- has no answers with a score > 0
- has no accepted answer
- has no pending reopen votes
- has not been edited in the past
9
days
... it will be automatically deleted:
This check is run every day across all sites.
See also: The official "How does deleting work? What can cause a post to be deleted, and what does that actually mean?" FAQ meta post.