You may want to receive email alerts before, during or after a case reaches a certain threshold that displays a particular case flag. If you have Enterprise or Unlimited Edition, you can accomplish this with time-based workflow. But if you have Professional Edition, you can accomplish the same using Escalation Rules which we will detail in this article.
Every time a Case Flag is set or cleared, the case is modified, which means that escalation rules are re-evaluated. That means that you can setup a rule that every time a case is modified and a case flag is currently set, an email will fire X hours later. One limitation of this approach is that subsequent modifications to the case that don't necessarily clear the flag will still reset the "clock" on when the email alerts will be sent. For example, say you have configured an escalation rule to email a manager 10 hours after a case flag is set on a case. If, for example, the subject or status is modified 5 hours later, the count down to 10 hours will start over again and the flag will potentially be displayed for 15 hours before an email is sent. While this limitation is important to understand, it is probably acceptable in most environments because the case still "received attention" within the specified period of time before an escalation occurred. The instructions below assume you have some familiarity with Escalation Rules. For additional information, consult Salesforce Help & Training.
1. Navigate to Setup > Customize > Cases> Escalation Rules and create a new (active) rule. Note that you can only have 1 active rule at a time.
2. Create a new Rule Entry as pictured below. You can set Step 3 (Business Hours) according to your organization's unique requirements. Save.
3. Add a new Escalation Action. Input the Age Over hours when the email(s) and optional reassignment should occur. Save.
Note that this is just a sample of how you can extend Case Flags with Escalation Rules and we recommend you consult an experienced Salesforce administrator to implement this.