The thing I find hardest to do by myself is evolving. Everybody define the evidence of evolution as a promotion. I believe that people should stop targeting promotions, and start targeting wisdom, knowledge and insight. As you start to focus on developing you knowledge and evolve by adapting greater knowledge the world around you will adapt. You won’t stay long in a mediocre job, if you are evolving this way. Either the job evolves with you or you get drafted to something new.
If you feel stagnation and feel bored doing something you love, you might just be at the upper end of a level, and need more input to get to the next. What level you are on does not matter, but give it a number for the fun of it, and write a paper about 4-5 pages about your own knowledge. Then start pro-active learning by buying some books. Dare to try the stuff you read about. Maybe you even need a coach to help you clarify where you are going. Put away the paper you wrote, hide it for 6 months or so. Before you review your paper, write a new one and then compare the two. You will then see if you succeeded to advance to the next level.
If you are an employer, when is the last time you bought your employees a book about the topic at your office? There are books about everything, even your trade. This example proves that you can find anything.
I want to become a better leader; I just bought four new books that I am currently reading trying to evolve to my next level of knowledge. But there is more that you can do. You can find video clips on youtube.com about anything. It is your obligation to try to find something. This one proves me right once more. You can find presentations about selling, learning, leading, motivation, building stuff and so on. Or you can always take some classes if you have time for it.
There is just so much you manage to read, watch or listen to, and if you have gotten to a high level, it might be hard to identify what the next level is like. At this point you most likely need a mentor or a coach to get you going further. But as I wrote at the beginning, I do not set a maximum level, as I believe there is none.