Good question! I think the "falling in love" part of stories is one of the best elements. That's why I'd recommend dragging it out as long as possible. That sounds strange (I don't think it's a good idea to drag out literally any other part of the story!), but have you ever noticed that in books and movies, the best part is when the characters are meeting and falling in love? Usually there's some drama ("will they? won't they?" type situations), maybe one of the potential lovers is already engaged, maybe the potential lovers have a fight or disagreement and these dramas keep things interesting-- but the moment they actually get together, the story falls flat.

So, in conclusion, I'd weave in with the plot to make it nice and long (but not boring, never boring!). I don't think it's a good idea to drag things out without any action-- whether the action is drama between the characters or, better yet, plot points that the characters face together.

I'm not sure what you had in mind for your story, but I hope this helps!