Hi Kate,

the correct use of times with depuis can be tricky. Here are the rules in a nutshell.

If stating something that has been happening for a while and still ongoing, you use depuis with the present tense:

J'habite à Paris depuis 5 ans. -- I have been living in Paris for five years (and I still live here).

In negative sentences where the action is already past, you use the passé composé:

Je ne l'ai pas vu depuis son départ. -- I haven't seen him since his departure.

You may use the present tense if you are referring to a (frequently recurring or habitual) action which stopped in the past:

Tu ne fumes plus depuis l'été dernier. -- You don't smoke anymore since last summer.

-- Chris (not a native speaker).