The perfect continuous aspect is used for the end of an ongoing action. How is it applicable in the two instances as follows?
I had been working in the office when 9/11 happened. (Here I worked even after the incident. This means the ongoing action never stopped.)
He will be tired when we meet him because he will have been exercising so hard. (Here as well, there is no implication that he will stop his exercise after the meet. That means he may or may not continue his practice.)
Thanks brp7