A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

File away leftovers
Planning a first draft
Part I. Research and writing: from planning to production

Once you have a first plan, you may discover that you have a lot of material left that doesn't fit into it. Resist the impulse to shoehorn leftovers into your report in the belief that if you found it, your readers should read it. In fact, if you don't have more leftovers than what you used, you may not have done enough research. File away leftovers for future use. They may contain the seeds of another project.