My Rom Com Question

As if there is only one! See, this is why I don't write Rom Coms. I just don't get it. I'm trying -- really. And, remember, all I want is to learn how to write better relationships, not map out seven beats of a Rom Com and write a romantic masterpiece from scratch -- not that a l'il lernin' would hurt me none.

So, I got a couple of books on Romantic Comedy and I put this question to our good friends on Wordplay and The Writers Building --

I am wondering what makes some Rom Coms timeless while others are forgotten before the credits finish rolling?

I understand that basic conflicts can either be written in a universal and multigenerational way or associated with something trendy that will eventually become dated. But dated situational reality doesn't necessarily rob a film of its charm, especially if the film's real focus is on relationships, so what is it that makes a once popular Rom Com grow stale while others endure? Is it because the film was written with the focus on the Com more than the Rom and the jokes grew old?

We'll see what wisdom shakes out of all this. Meanwhile, I'm out of time. I only have a couple of days to do some last minute polishes and get my newest stuff off to my agent this weekend because Monday, I go back to the trenches and who knows how much screenwriting time I'll fit in between what's already on my calendar and the lamentable "getting to know you" curve during the initial month or two on a new job.

First things first. New clothes? Clean briefcase? Box up pictures for the office walls? No. Complete my outlines!