Some call this process ideation. Others call it research. In the book, "Finding the Next Steve Jobs: How to Find, Hire, Keep and Nuture Creative Talent" by Nolan Bushnell and Gene Stone, the process is referred to as "preloading".
What is preloading?
One page 177, Bushnell and Stone write:
"When tasking a group of creative people, give them a heads up on their next projects. Their endlessly functioning, hyperactive minds will immediately start thinking about the future, even as they are still working on their current projects."This is sound advice. It works for many creative people, whether they are working on books, movies, music, or engineering projects. For example, for the past five years I've been reading many articles on stormchasing along with watching endless hours of footage. Besides being a field of interest, there was a certain amount of preloading going on...even though in the meantime I was working on other ideas.
The great part about this technique is that even though the current main focus may be an important project, the brain has a remarkable capability to work on multiple concepts at once. Some problems are best solved with time and an ample amount of information being "fed in" via articles, books, trips to the art museum, observation, etc. Although a solution may not appear immediately, many times the brain is working on the answer in the background. Then one day the answer may appear "out of the blue" complete or nearly complete.
Where it gets interesting is when one can preload information about several different ideas/projects ahead of time. If those projects are interrelated or any connected somehow, all of the projects may benefit. Along those lines, there is also something to be said for writers who specialize in a certain type of fiction or non-fiction. Researching the next book may build off of what they already know or have discovered during the process of writing their last book, which benefits the reader and saves time.
Of course the flip side to all of this is that it is easy to get carried away with research, especially if that future research is more interesting than what you are currently working on. At that point I suppose it becomes "preload overload". The main thing is that it is can be a great way to work and can build a creative person's confidence as well as giving them goals to aim for.