I suppose if your idea of complete spiritual growth is "stop once I've done a few things," then you're indeed finished, and you can rest easy. There's nothing left to do. Go have some ice cream and watch American Idol.
On the flip side, if your idea of spiritual growth is to keep learning and evolving, and to constantly expand your knowledge and experience base, then yes, it's an ever-changing process. Look at it this way: by the time a child finishes kindergarten, she's learned how to write her name, count to ten, tie her shoes, and share with her friends. These are all valid and useful things to know so in theory, we could all stop going to school after kindergarten. However, if we stay in school and continue to learn and evolve, we'll learn all kinds of new things. In fact, we'll learn things we didn’t know we needed to know.
Spirituality is like that as well. You can read two or three books you found in the library, light a candle and rename yourself Moonwolf Puddlefairy and call it a day. Or you can read more books, including ones you've never heard of, and you can try new things and you can experiment with stuff you never thought you would experiment with. You can step outside of your comfort zone. You can meet new people -- many of whom are going to challenge you and ask you why you're doing things a particular way.
If you someone who decides you'd like to study in a group setting, such as a coven, are you going to be patted on the head once your year and a day is up, and told you're all finished and here's a pretty certificate? No. You're going to be expected to constantly do and try and learn new material. Why? Because to really obtain knowledge, you have to understand that knowledge is not a finite thing. In other words, there's always something new to learn. You don't know everything, and you never will.
Why did you decide to become Pagan in the first place? Think about this for a moment, because people do so for a variety of reasons. Some people come into Paganism and Wiccan thinking it will be a walk in the park -- and probably way easier than their last spiritual path. But it's not, and that's okay. Many things worth having are worth working hard for. Put forth some effort, dedicate yourself to growing, and don't expect things to be handed to you on a silver platter. Because if you think you're all done because you read a book and lit a candle, that's not Paganism or Wicca. That's stagnation, and you'll never go any further than where you are right now.