I think it is true, but not because you have nothing more to learn when you're experienced, but that there are fewer and fewer people on SO to answer the questions that you encounter when you get more and more experienced.

I've answered about 200 questions. I've asked two, and both remain unanswered to this day. One of them had comments from someone who clearly was out of their league but wanted to be helpful. The people who could've answered those questions are not (or were not at that time) on SO.