I can't really pinpoint any particular scene in any of my wips that I thought would never end. If it was a long scene, I was probably so enthralled in writing it I wasn't thinking "Gee, is this ever going to end?" I mean, as much as I like reading, even I can't stand a long scene unless it's a good one that keeps you engrossed in it.
For the most part, as I write a scene I keep a few points in mind. I need to make it a good one, and hopefully have it contribute to the story in some way if it does turn out to be a long scene. And if it isn't, then I try to leave a reader hanging by a surprise twist. I've written a lot of short scenes in my work that give me chills, and leave me giddy. At the time when I wrote it, even I couldn't wait to get back to it and see how everything turned out.
And that to me is a huge reason I write. You are the one in control, yet at the same time, you're not. You're driven by some unseen but very much felt force that guides you as the words flow. You somehow get these wonderful ideas then when you finally get the chance to execute them in a storyline, and get a feel for the characters you just let them take over the story.
This is why I truly believe authors do not choose their stories. The stories choose the authors.