I'm what is known as a 40-year overnight success.

Things that look like an 'overnight success' typically are not.

It takes 20 years to make an overnight success.

Actually, I'm an overnight success, but it took twenty years.

There's no such thing as an overnight success. It took me a long to get there.

I was 40 years old before I became an overnight success, and I'd been publishing for 20 years.