When do we use Future Perfect Continuous?
Duration of activity up to a future moment
Future Perfect Continuous emphasises HOW LONG an activity will have been going on by a specific future moment. It combines the idea of duration (like Present Perfect Continuous) with a future deadline (like Future Perfect).
How long an activity will have been in progress by a specific future time.
By the championship, Max will have been training for six months.
"by the championship" + "for six months"
By next year, I will have been studying chess for three years.
"by next year" + "for three years"
By the time you arrive, I will have been waiting for an hour.
"by the time" + "for an hour"
The focus is on the PROCESS and its duration, not the completion.
By 5 pm, she will have been working for eight hours. (still working at 5 pm)
process still ongoing
By 5 pm, she will have finished work. (completed by 5 pm)
Future Perfect = completed result
Future Perfect Continuous = DURATION up to a future moment. Future Perfect = COMPLETED action before a future moment. "By then, I will have been studying for 3 years." (duration) vs "By then, I will have finished the course." (completed)