Almost without exception every bonsai question can be answered with the phrase "well, it depends."
When should I fertilize my bonsai?
When should I water my bonsai?
What is the best time of year to wire my tree?
Should I remove this branch?
Can you really grow a tree in nothing but marbles?
Well, it depends. The main thing to ask yourself is, what am I trying to accomplish? What is your ultimate goal and what is the best way to accomplish that goal? Careful observation should lead you in the direction of the appropriate answer.
I often try to avoid the what/when/how/where questions when asking for advice. It is often an opinion on the course of action that I am looking for when I have a question. My questions are often in the form of "if I remove this branch and then wire the one above it into position would that fill the area appropriately and provide a natural and pleasing shape?" This removes a lot of the follow up questions that my advisor might have and gives him or her the insight into what my intentions are.
If you have a young tree, or one that requires a lot more growth, plenty of fertilizer and unrestrained growth are the answer. Often the first response to the "what should I do with this tree" question is to put it in the ground for a number of years. What this answer is truly saying is that this tree is far too young in it's development to worry about refinement or restraining growth. If you start the refinement process (pinching, etc.) too early on this tree you will have a well ramified branch on a slender trunk that lacks movement, taper, and character. At this stage you must keep the tree alive and well fertilized. Roots can (and should) be worked on during this phase, creating the structure for future development.
Now you have grown or perhaps you've purchased a tree in this category of the approximate size you want. Now what? By this time you should have examined the roots and come up with a plan for the future. Perhaps you've identified a taproot that you will remove over the next few years. The trunk has good movement and character and has pretty good taper from nebari to apex. Now you can start to select the branches that you've been eyeing during early development. Remove completly unwanted or unneccessary branches. Don't concern yourself too much with the "rules" during the early parts of this work. If you remove every branch from the inside curve of a bend you may severly limit your design choices. Look to the future of your design, but don't tie both hands behind your back, and certainly don't risk the health or your tree. And remember, fertilize, fertilize, fertilize.
Okay, it's not ready for Kokufu but this tree is starting to look like a bonsai. This year's club show just passed, which means you've got almost a year to get everything done. You don't think the tree will be ready in just 12 months? Okay, wait an additional year. On fast growing trees such as maples and elms you could quite possibly be ready for the show next year. Stay on top of pinching, pruning, and wiring and you'll be amazed at the progress. It may take a few additional seasons to get well refined branches from species such as pines, but the ultimate goal is the same. Careful timing of fertilizing, pinching, and pruning is required here. Well worded questions to local experts and an idea in your head should get you the appropriate answer if you still need guidance.
Your tree is finally show ready and you plan to make a big debut of all your hard work. The tree has been finely wired to the tips of each well ramified branch. The pot that you recently selected complements the tree in shape, color, finish, and texture. The soil is cleaned of debris and a top dressing of short, neat, health green moss has been applied to the surface of the soil. Several options for stands have been selected and you're waiting for show setup time to make the final choice based on the lighting, height, balance, arrangment, and personal preference. Watering and fertilizing has been carefully monitored over the last several months so that growth is in check and internodes are short. The tree is the healthiest it has ever been and you can't wait for the other club members and visitors to the show to see your beautiful tree.
It may not be feasible to keep the tree in show-ready state for many years in a row. Pretty soon the health of the tree may start to decline. It would be far better for the tree to have a period of rest. This would be a great opportunity to examine the tree and perhaps rework some of the branches. Some of the larger or more coarse growth can be replaced by finer, more refined branches which will most likely increase the quality of the overall design. Your choice now is to decide how much to remove and how drastic a change you want to create. It may be a few years before the design is realized, but you've got the time. Besides, you've been working on several other trees and one in particular is just about ready for the big show. Focus your efforts on this new tree while the other recovers.
How long did all of this take? Well, it depends!