If its not too late to weigh-in, let me share my experience. It may make you feel better, it may make you feel worse.
In the Spring of 2000, I started working on what I thought would be a straight-forward novelization of a somewhat over-long screen play I had drafted in film school. 19 (!) years later, I'm still at it.
Now, in the intervening years, I've had a busy career, raised two kids, and squandered much time and money on old cars with needs. That "straight-forward novelization" I envisioned, steadily grew and developed meanwhile. After literally dozens of full re-writes, it is now a five-part epic--and I am still editing. At current, the series totals just over 500,000 words; but I estimate that I have actually written at least 2,500,000 words over the course of those 19 years. (My "Delete" key gets heavy use.)
I have gotten notably faster and more disciplined with time. I just am currently starting a major re-write of Book III, replacing upwards of 90% of the entire text with new material, and I expect to be done sometime in the Fall.
Someday, I might even convince someone to publish the damn thing. Even then, I suspect I might leaf through a print copy on a bookshelf and say to myself: "oh, I know how to make this better . . . "