jg8u12,
As the tool is currently designed there is no way to accomplish this type of follow up notification. I don't even believe it to be possible through the creation of custom work flow as that would require one to capture the time frame that the change to that status occurred and then after the 72 hour period to generate an automated email to the defect assigned user. However generally the workflow requires an action to trigger the workflow to occur (such as the entering or exiting of a module, updating an entity, etc and this would be triggering on its own without user intervention in such action so I don't see it possible to have the workflow initiated unattended.

Unfortunately, it would seem that this is not possible even as a workflow creation and it is definitely not possible for the standard ''out of the box'' configurations,
Dan