@DiegoPalacios just said a good piece. So I'll just add my personal thoughts on your questions.
I guess I only get really frustrated when a couple gets together, then they break up... then they get together THEN THEY BREAK UP and etc.
It really bums me out when the story keeps going back and forth to pad its length. Ross and Rachel are the classic example, but I'm thinking other series like Arrow or manga like Fushigi Yugi. Of course, since you control your comic and it's not a victim of TV ratings extending your story, you can easily avoid this. Of course, unless the movement makes sense to your story, who knows, but I can't remember one in which I like this kind of stuff.
The problem with these kinds of stories are the ''artificial drama'' they create. External problems that exist solely to keep the characters apart so the plot can go on. It always feels hollow to me.
Every story has this natural flow to it, so respect that. If the couple gets together early on, work with it, not against it. Well, maybe a little against it. Organic drama is always cool.
Personally, I don't mind at all. I love a good hybrid.
Again, it's been years since I read it, but I liked Fushigi Yugi a lot when I was younger and I liked it as much for the lore and battles as for the ships. It's a shojo romance manga, but I loved the action in the back.
So yeah, I dig it.