How long have you been going to the same school?
I've been going there since / for...
How long have you been studying English?
I've been studying for / since...
How long have you been wearing the same watch?
I've been wearing since / for...
How long have you been living at the same place?
I've been living there since / for...
How long have you been doing your favorite hobby?
I've been doing it for / since ..
How long have you been wearing the same hairdo?
I've been wearing it for/ since...
How long have you been dating your boyfriend/girlfriend?
I've been dating for / since...