The future perfect continuous tense is formed with the future perfect tense of the verb to be (shall/will have been) + a present participle (verb + -ing). 

The future perfect continuous tense is used:

to indicate the length of time that an action continues in the future.

Examples:

  • At noon tomorrow, my uncle will have been driving a hearse for fifteen years.
  • My uncle will have been researching in Antarctica for exactly ten years next Sunday.

 

to show an action in progress until an event happens in the future. Here, a time clause is used. The future perfect continuous tense may come either before or after the time clause.

Examples:

  • By the time he comes home at the end of the year, he will have been studying overseas for five years.
  • He will have been studying overseas for five years by the time he comes home at the end of the year.
    (Time clause: by the time he comes home at the end of the year; main clause: he will have been studying overseas for five years. A comma is placed at the end of a time clause when it comes before the main clause.)