I have a limited capacity for certain types of fiction. Horror films tend to lose me after about 30 to 45 minutes. Comedies - wacky, zany, follow-the-joke-and-never-mind-the-logic-comedies - I normally enjoy for about an hour. And I have a very small amount of tolerance for romances.
All of this is for bog standard, low quality stories. A horror film with a bit more to interest me - Saw, with it's central mystery, or Scream with it's references to other Horror films; both of which, by no coincidence, have above average acting and directing - I've happily sit through.
But I was talking about romance. Let's consider for a moment The Break-Up.
If you've not seen it, the title tells you the premise. The interesting thing is that the romance which precedes The Break-Up is shown in a set of photos which form the credit sequence at the start. And I enjoyed it. No, really. See, any on-screen romance story which lasts under about 5 minutes is fine with me.
I would put the video to David Powter's Bad Day here, but, although the song has been (mis)used by several people on Youtube, I can't find the actual video. So let's jump straight into the murky depths of Pirates of the Caribbean fandom with this video of Captain Jack Sparrow/Elizabeth Swann moments to Thea Gilmore's cover of the Buzzcock's Ever Fallen in Love.
No, go and watch it and if you're sick of it before the end, you've found your limit (or maybe you don't like Thea Gilmore, in which case we don't need your patronage round here any more. Go on, move along).
Note that, good acting, plot, characters, etc. etc. will immensely increase my attention span. But if you want me to sit still for a feature-length generic sub-Catherine Cookson period family drama/romance, I may be a little tetchy at the end.
Or just dozy maybe.
 It's a failure of communication. However, the failure of communication both arises from and illuminates the characters, rather than being just decided by authorial fiat (which is why I can't watch soap operas).
 Based solely on a very bad Youtube video, which has all the Batman/Wonder Woman romance scenes from The Justice League cartoon, to the sound of Phil Collins' Against All Odds, one of my friends has a much shorter attention span for random romance.
 Also the Bruce Wayne/Diana Price scenes. Since I've not watched it, I don't know whether their secret identities are shared. For more on the flimsiness of Bruce Wayne/Batman identity, take a look at Justice League International #16 ("His name is Wayne... Bruce Wayne")
 Will Turner? Is he any relation?