Whenever I've hit my maximum autonomous capacity, I asked myself what else could go wrong in the scene, what could make it more interesting, or what would happen if I threw in a completely different character. Usually trying to find what could make it go wrong open the whole new Avenue of writing fodder. Because you have to explain why it went wrong, how it went wrong, and then deal with the aftermath. That usually should allow you to extend your writing all the way up to an hour.
whether you keep the scene or not doesn't matter at that particular moment : what matters is your writing.