Now as far as the whole "rewriting previously written stories" go, I've only done this twice. One is something that became a series and I managed to get 4 1/4 books done in a year and a half (729,589 words total by the time I stopped 1/4 the way through book 5).
BTW, this is still to-date my greatest life achievement. I wrote each book in subsequent order, taking anywhere from 1 month to 4 months for all of these books.
I have never managed to repeat this godly act in the...2 or 3 years since.
In the past six months, I decided to rewrite the first book because it felt so...juvenile in comparison to the other 4 books that it didn't sit well with me.
But, as often happens to people like me, while attempting to change some stuff here and there, SO much was changed that I've basically had to rearrange or completely change the course of events for all the other books now as a consequence.
My second attempt at rewriting was when my brain was just sort of on autopilot at work and bored. I was slicing bread (cause I break bread and do a buncha mundane tasks all day which means I think about my stories in order to entertain myself and stop death via boredom out of sheer desperation!) when my brain suddenly started up a mental conversation.
Brain: Hey, so, you remember "In the Shadow of Wings"?
Me: Uh...yeah? You mean the story I haven't touched since I was fifteen?
Brain: Yeeeah, that one. So, what if it was done in modern times instead?
Me:...! W, wha—?!
Brain: Um, also, what if you gender-flipped them?
Me: I...is such a thing even possible?!
Brain: What else? Oh, yeah, also, how about if the kid's an actual dragon? You know, hatching out of an egg and everything?
I swear, my brain is such a jerk sometimes!