I understand from the disucssion that you can use depuis with the present tense or passé composé but I have this question:
Depuis quand est-ce que vous êtes vous mariés ? ( a point in time in the past)
Asking a person who is married how long they've been married (and still are): Vous êtes vous mariés depuis 30 ans? (Past tense so does this mean they're no longer married?) or, should you say, Vous êtes mariés depuis 40 ans? (still married).
This always trips me up so thank you ahead of time for your help!