Based on what I've seen, I don't think it's abnormal, necessarily. I used to take a creative writing class, and I was actually told the opposite. We were told to read over every chapter and revise it if we ever decided to get into writing books.

My instructor said he was working on a book- he was pretty much always typing away on his laptop when he wasn't going over our assignments. Someone at the front of the class asked if he could read a sample of what he had, and it sounded great. I was especially blown away.

But he told us he wouldn't be finished for a while, and at that point he was six years into writing that story. He said that if any of us get into writing, to expect constant revisions and not just as we're typing, but even after we reach the end of the story.

I'm sure there are writers out there who don't give their stories a second thought, or do minimum revisions. But I also think it takes luck for those stories to do well. The amount of effort you're actively putting into writing the story just means you aren't relying on more unpredictable factors in the future for them to be properly received.

You're taking every part of your work into consideration, so that it finishes in a way that's satisfying. That's completely normal with any craft.