I find it hard to conceive a mature artist who (regardless of age) isn’t already a mature person. I suppose it comes down to what has already been mentioned about experiencing life. Art in in my mind is all about communicating what we as individuals experience in our lives. Communicating thoughts, ideas, notions, emotions, fears, hopes and dreams.
In art, as in life we are always learning. By recognising the value of constructive criticism and the useless value of groundless negative feedback, the mature student of art and life can progress and grow. Someone without maturity (be they an artist or not) will hamstring their own emotional development by reacting defensively against any and all criticism, and not perceive the lessons to be learned before them.
If you don’t get out there and live life every now and again, it is real easy for your work to stagnate, even though it may be technically ok.
As for style…I think even that changes and develops with you. Especially if you work digitally, due to the huge amount of advances and approaches available.
Having just gone through some major changes in my life, I have been re-assessing the way I approach life and also how I create my artwork. I see both as being interconnected on all levels.
I have also re-discovered that rather than do the “correct” thing all the time, its fun to be pretty immature and reckless sometimes! You never know what you may stumble upon. 