Usage
The past perfect continuous is partly like the present perfect continuous, but it refers to a continuous action that was finished at some point in the past.
More Examples:
I recognized that I had been doing nonsense things to change her.Jim and Laura had not been working at the same place for years before they saw each other last month.
He had been waiting for me for hours before I came.
Had you been studying Spanish for 7 years before you moved to Spain?