Because it takes someone ten years to write a book does not mean that writer put in one minute more time than someone else who wrote a book in a month. I know one well-known literary write who has made a big deal of publicly saying it takes him five years to write a novel. It doesn't. He does all sorts of other things for four and a half years, and then wrote the book in six months.
The simple fact is that many, many of the best writers in history wrote extremely fast, and were extremely prolific.
I'm not at all sure that practice does make perfect, however. Writing is not like shooting jump shots, or just about any other example given. It sure as heck has nothing to do with ten thousand hours of practice. If it did, about 99% of the famous writers throughout history would still be unknown.
There is no reason at all why you can't have bot quality and quantity. There is no reason at all why you can't write an extremely good first book very fast. Except for a pesky little thing called talent.
Writing very fast does not mean hack work. Only very slow hacks thinks this. Shakespeare certainly wouldn't agree. Neither would any one of a thousand other famous writers.
It does not take twenty years to write a good novel. Or ten years. Or five years. And a novel is no better for taking twenty years than for taking twenty weeks.
A novel is good because the writer has talent, and simply knows how to tell a good story, and fill it with good characters.
The point, I think, should always be to sit down and write. Don't pretend that endlessly tinkering is writing, or that thinking for six months about how to rewrite that scene in chapter twelve is writing. Practice may or may not make perfect, quantity may or may not help because you may or may not have the talent to make it mean anything. But it sure as heck can't hurt, and you'll be doing what everyone else claims to be doing, which is actually writing.
