I have John Truby's book on screenwriting The Anatomy of Story, and in this video of his at 6:50: He talks about how there has to be enough time give to the love subplot in order for the main character to really be felt with by the audience. At the same time though, when you want to keep your script at a good length and not go overlong, you don't want to spend too much time on it either, especially if it's just a subplot and not the main premise, if that makes sense. He says in the video, you cannot montage love but there have been movies that have done it. The best example I can think of is The Godfather. Michael and Appolonia go on one date, and then the next scene you see them in they are married. This was enough for audiences to be satisfied before Appolonia's death, so I am wondering if it's okay to break a rule, what should I keep in mind?