Ответ:

1. ...for 2 years (или любой другой промежуток времени)

2. ...since we were 7 years old.

3. ...for 20 years (или любой другой промежуток времени)

4. ...since the 90s.

5. ...for 3 years (или любой другой промежуток времени)

6. ...since i was a child.