The concept of prolongation in Schenkerian analysis broadly describes the elaboration of a vertical sonority. Among the most basic ways to prolong a chord is by arpeggiating it, such that it governs the time span of its arpeggiation. In Heinrich Schenker's writings, however, there are many examples where the prolonged chord differs from the one being arpeggiated. Many of these involve a downward arpeggiation of a triad from fifth to root that connects two different harmonies. This article examines the prolongational issues involved in this type of arpeggiation. The first section seeks to explain Schenker's understanding of these progressions within the context of his approach to prolongation in general. The next section revisits those very issues that Schenker grapples with in his analysis of these progressions, and considers the role that different parameters have in determining the prolongational boundary between the first and the last chords of the arpeggiation. In examining the prolongational issues surrounding downward triadic arpeggiations, this article promotes a more dynamic approach to prolongation.