It takes at least as long to become a master practitioner. One must learn to identify the fundamental structure and form of a potential bonsai, selectively ignoring tangle or sparseness. The master uses rules of style as guidelines only. He knows that rigid adherence often leads to disappointing results. Training is a process of refinement.
First consideration is given to the trunk.
It may take several years to obtain an appropriate taper. Next, the main branches are refined to provide the general shape of the canopy. This too may require several growing seasons to accomplish. Finally, the branchlets are tended and the bonsai is fully revealed. He knows that it is the back which provides the depth required for a dramatic frontal view.