过去完成进行时由“would have been+现在分词”构成。
He said that by the end of the spring term he would have been studying English for three years. 他说到了春季学期末，他就学了三年英语了。
I want you thinking of food and wine, because these last years would have been miserable for you. 我要你只想吃喝，因为最近几年你的生活够苦的。
I know by this time next week you’ll have been working here for 30 years.
→I knew by that time he would have been working there for 30 years.
She will have been teaching in this university for 20 years by this summer.
→She told me she’d have been teaching in that university for 20 years by that summer.