Plasma cells in human bone marrow (BM PCs) are thought to be intrinsically long-lived and to be responsible for sustaining lifelong immunity through the constitutive secretion of antibody--but the underlying basis for this serological memory remains controversial. Here, we analyzed the molecular persistence of serological immunity by an examination of BM PC immunoglobulin heavy-chain (IGH) transcripts derived from serial bone marrow specimens obtained during a span of several years. Using high-throughput sequence analysis of the same individual for 6.5 years, we show that the BM PC repertoire is remarkably stable over time. We find that the bias in IGH V, D, and J individual gene usage and also the combinatorial V-D, V-J, D-J, and V-D-J usage across time to be nearly static. When compared to a second donor with time points 2 years apart, these overall patterns are preserved, and surprisingly, we find high correlation of gene usage between the two donors. Lastly, we report the persistence of numerous BM PC clonal clusters (~2%) identifiable across 6.5 years at all time points assayed, supporting a model of serological memory based, at least in part, upon intrinsic longevity of human PCs. We anticipate that this longitudinal study will facilitate the ability to differentiate between healthy and diseased antibody repertoire states, by serving as a point of comparison with future deep-sequencing studies involving immune intervention.