Future perfect progessive

Future Perfect Continuous
Future Perfect Continuous has two different forms: "will have been doing " and "be going to have been doing." Unlike Simple Future forms, Future Perfect Continuous formsare usually interchangeable.
FORM Future Perfect Continuous with "Will"
[will have been + present participle]
Examples:
* You will have been waiting for more than two hours when her planefinally arrives.
* Will you have been waiting for more than two hours when her plane finally arrives?
* You will not have been waiting for more than two hours when her plane finally arrives.
FORMFuture Perfect Continuous with "Be Going To"
[am/is/are + going to have been + present participle]
Examples:
* You are going to have been waiting for more than two hours when her plane finallyarrives.
* Are you going to have been waiting for more than two hours when her plane finally arrives?
* You are not going to have been waiting for more than two hours when her plane finallyarrives.
NOTE: It is possible to use either "will" or "be going to" to create the Future Perfect Continuous with little or no difference in meaning.
Complete List of Future Perfect Continuous FormsUSE 1 Duration Before Something in the Future

We use the Future Perfect Continuous to show that something will continue up until a particular event or time in the future. "For five minutes," "fortwo weeks," and "since Friday" are all durations which can be used with the Future Perfect Continuous. Notice that this is related to the Present Perfect Continuous and the Past Perfect Continuous;however, with Future Perfect Continuous, the duration stops at or before a reference point in the future.
Examples:
* They will have been talking for over an hour by the time Thomas arrives.
*She is going to have been working at that company for three years when it finally closes.
* James will have been teaching at the university for more than a year by the time he leaves for Asia....