1) Our writers are evaluated as often as possible to make sure we deliver only top-notch orders. We also frequently shuffle the "Advanced" writers to have the best ones on their team. Our real-time rating system takes every order a writer completes into account, selecting a true match for such an elite team. The latest evaluation of skills or changing average scores may be the reason why they spend some time on the regular team and some time on the advanced team.
2) We evaluate our writers on a regular basis to make sure they deliver quality papers that correspond to their category. Thus, some of them may be transferred from the "Best available" category to "Advanced" and vice versa. Once a writer completes an order, our real-time rating system updates his or her score. That's why a writer you worked with before may belong to a different category.