"How long" were they together? is it correct? I can use "how long" + past tense?
Thanks for your reply.
Yes, that's fine:
"How long were they together?" (they are no longer together)
"How long did you know him?" (he is dead)
"How long did you go out with her?" (you have stopped going out with her)
"How long did it last?" (it has finished)
"How long have they been together?" (they are still together)
"How long have you known him?" (he is still alive)