Is reuse of "internal" results considered self-plagiarism if used in a later publication?
From my experience, researchers are free to re-use a given dataset as many times as they want in numerous publications. I've been involved in single datasets (which, admittedly, took years to build) that generated dozens of papers, and that is by no means a unique scenario. My understanding is that researchers are to refrain from publishing an identical analysis on an identical dataset in different papers. If you're using a single dataset for multiple analyses, there's no need to re-generate the data.