Grammar - Future Perfect Continuous

The FUTURE PERFECT PROGRESSIVE TENSE indicates a continuous action that will be completed at some point in the future. This tense is formed with the modal "WILL" plus the modal "HAVE" plus "BEEN" plus the present participle of the verb (with an -ing ending): "Next Thursday, I will have been working on this project for three years."

Generally, progressive forms occur only with what are called dynamic verbs and not with stative verbs. If you wish to review that concept now, click HERE.

Singular    Plural
I will have been walking    we will have been walking
you will have been walking    you will have been walking
he/she/it will have been walking    they will have been walking

Singular    Plural
I will have been sleeping    we will have been sleeping
you will have been sleeping    you will have been sleeping
he/she/it will have been sleeping    they will have been sleeping

Singular    Plural
There is no future perfect progressive for the "to be" verb. "Will have been being" is expressed simply as "will have been": "By this time next year we will have been being on this committee for a decade."

By the time he finishes this semester, Gesualdo will have been studying nothing but parasites for four years.
Will they have been testing these materials in the lab before we even get there?

http://grammar.ccc.commnet.edu/grammar/tenses/future_perfect_progressive.htm