It took me 15 years of development to start feeling like i really knew what i was doing (eventhough i have a CS university degree), and i keep understanding new things every month on my job. And that's just the coding part, i'm not even mentionning the human aspects when working in a team.
The way i analyse a problem, approach technological solutions, design system architectures, pick a programming language, are all extremely different from how i did it 5 or 10 years ago.
For a lot of us, software development is much more similar to craftsmanship than breakthrough scientific research.