This is one of the longest tense forms in English. It is not, however, one of the most common.

The Future Perfect Continuous Tense

(time) + will have been …ing
or
will have been …ing + (time)

-examples

By the end of the year, this school will have been teaching classes for 20 years.

The Passive Voice

To make the passive voice:
be (in correct tense) + p.p.

In the future perfect continuous tense, this is:
(time) + will have been being + p.p.
or
will have been being (done) + (time)

– example

By the end of this year, classes will have been being taught by this school for 20 years.

Examples of the future perfect continuous tense in the passive voice

(active) By the end of the year I will have been reading this book for 6 months
(passive) By the end of the year this book will have been being read by me for 6 months.

(active) They will have been painting houses in this town for 5 years by the end of this year
(passive) Houses will have been being painted by them in this town for 5 years by the end of this year.

Exercises

1. Change these sentences into the passive voice:
(i) By the end of this week, the police will have been chasing them for 2 years.
(ii) By this time next month, I will have been running this company for 25 years.
(iii) They will only have been reading this book for 2 weeks by the time the exams start.

2. Change these sentences out of the passive voice:
(i) By the time the artists have finished, the model will have been being painted for over 3 hours.
(ii) The suspect will have been being followed for 3 months by the end of this year.
(iii) By the end of this week the car will have been being fixed by the mechanic for 2 months. It’s too slow.