Create a Saved Case Search Based on Case Aging

To create a saved search for cases that were closed in X days or less:

In this example, let's take X days = 7 days.

1. Navigate to Lists > Search > Saved Searches > New
2. Click Case
3. Enter a Search Title
4. On the Criteria tab > Standard sub tab, add the following:

Status is Closed
Formula (Numeric). In the Formula box, paste this formula:
CASE WHEN (ROUND({closed} - {createddate}) <= 7) THEN 1 ELSE 0 END

Formula (Numeric) "equal to" Value 1

5. In the Results tab > Columns sub tab, add Date Created, Date Closed, Status, and other fields that you would like to display when running the search.

6. Save&Run.