The first quilt I made was for my sister, many years ago. It was a very simple quilt, but it took a long time. After that, I started making baby quilts - they'r'e a lot smaller, but they still took a long time.
These days, I make far more complex quilts, and it takes me a lot less time.
There are a few reasons for that. Of course, just being more familiar with the process makes a difference.
I also have better tools - I got a cutting mat and rotary cutter a couple of years ago, and that helps make sure everything is straight.
I've also learned when to rip out the stitches. When something is really wrong, there's no amount of ignoring it that will work, and procrastinating will just mean it's a bigger mess to undo.
And finally, I've learned that that most mistakes are fixable. On my niece's quilt, several of the squares were too small, so I added complementary fabric around the edges. Yes, you can still see where the problems were, but it looks good and she doesn't care.