That moment when you overextend a story because people like it

I'm talking Pony-Me^TM here. It was literally supposed to be maybe a 5-chapter or so one-shot, but what happens instead?

I begin building more and more into the story, pushing the ending further and further back, to the point where I'm quite confident that this'll last at the least a good 15+ chapters, complete with 3 planned endings that branch off chronologically, and an entirely new writing style that was meant only as an experimental tweak.

So...