I've noticed rewriting early chapters seems to take so much longer than later chapters. I wrote and rewrote and rewrote again chapter one of book one of my chapter book series, Doomimals. I seriously spent five to ten times longer on it than I did on all of the others because I needed to make sure it did all the important things: establish the characters and why the reader should care about them, establish the setting, stick my toes into the adventure that was about to hit like a tidal wave, show the characters making decisions that would lead them out of the normal world and into the metaphoric underworld, and make it all seem engaging and fun. That's a lot for one chapter to carry. And it all had to be done in as short a space as possible, so the reader would keep reading.
I've now gone through the first chapter and made sure, as writing experts say, it ends not where it did end, by getting into the adventure with a new set of characters, but on a cliffhanger that hints at the adventure to come. I'm now working on making sure chapter two is as compelling and engaging as it can be. I want to make sure the character is consistent, funny, and endearing, as with the main character of the first book. In short, I'm working hard to make these books as fun for you as I can.