Is reuse of "internal" results considered self-plagiarism if used in a later publication? This is a little bit different from the case of reusing boilerplate text.

Say one has done a series of experiments (either real or "virtual") to produce a set of results. Because the results are inconclusive as to the cause of certain effects, an additional, much larger set of experiments were performed under a series of different conditions to complete the "factorial matrix" of possibilities (all possible states of factor X crossed with all possible states of factor Y).

However, because the original results are valid, and represent unique "cells" in the factorial matrix, is it necessary to rerun the experiments for a future publication, or is it just a matter of obtaining journal permission for the re-use of figures and tables associated with the presentation of the data? As an example, am I violating copyright if I add a new set of curves to a figure which contains the same data as before? 

I ask in part because there was just today a retraction based on reuse of figures, and I'd rather not run afoul of guidelines.
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.