it will take a little finagling to do this.
on the login page, edit the security assist authenticate user behavior, on the session tab, click the plus button to store the Group ID in a session variable.
you will also need to uncheck the Go To Previous page if it exists option.
next, on the login success page, create a recordset to query the groups table and use the groupID Session to filter.
you can then save the groups expiration date to another session.