How long have you known your best friend?
I've known your best friend for ten months.
How long have you been building the websites?
We've been building websites since we were twelve.
How long have you been class president?
I've been class president since last month.
How long have you owned a laptop?
I've owned a laptop since September.
How long have you been collecting comic books?
We've been collecting comic book for a long time.
How long have they been studying ballet?
They've been studying ballet since they were five.
How long have you been volunteering at a soup kitchen?
We've been volunteering at a soup kitchen for a long time.
How long have you had a smartphone?
I've had a smartphone for one week.
How long have you liked mystery novels?
I've liked mystery novels for two years.
How long have you been living in Paris?
We've been living in Paris since we were ten.
How long have you belonged to the judo club?
I've belonged to the judo club since 2009.
How long have you been playing the saxophone?
We've been playing the saxophone for a long time.