At the moment, admins have to manually manage license removal for inactive Enterprise users.

1. On the org level, admins can deactivate the account and this will free up the licenses taken up by the site.
2. On the enterprise site, admins will need to revoke the Enterprise application license manually. This needs to be done for the same user on multiple Enterprise site in the organization. 

This gets to be a huge effort to free up enterprise/product licenses when there are thousands of accounts and multiple  sites involved. 

Suggestion :

Allow policies based on end user inactivity

• Deactivate accounts that has not been active anywhere for X days
• Revoke license on site level if the user has been inactive for X days on the application.