You can trigger an automation based on the number of days that have passed since an update was posted by a colleague about a contact.
Number of days that have passed since the contact was tagged in a story  | is greater than or equal to a certain number |
How to turn it on
Select Create in the top menu
Select Automation
In the Criteria dropdown list, scroll down until you see Days since last update by a colleague
In the Is field: set it to greater than or equal to
In the This field: enter the number of days
Choose the Automation Actions you want to run when this criteria is met for a contact
Scroll to the bottom and press Save.