The slow approach to equilibrium concentration indicative of non-Fickian diffusion in polymer composites necessitates experimental time frames which are often of limited feasibility. As a result, experimental studies are terminated prematurely due to time constraints or incorrect identification of equilibrium. Here, the three-dimensional anisotropic diffusion behavior of a six, twelve, and forty-ply quartz-reinforced bismaleimide laminate is quantified through a five-year, full-immersion gravimetric absorption study. The applicability of the three-dimensional hindered diffusion model is investigated, while projections of future absorption behavior made at 21 months are revisited in light of three years of additional data. The mathematical equivalency of the hindered diffusion model and a diffusion-relaxation model under certain conditions is discussed. Moisture content rises continuously throughout the five-year experiment for all samples. In the six-ply case, the standard termination criterion for the equilibrium condition is met before six months and 1.38% moisture content by weight. Actual moisture content reaches 1.56% after five years. The hindered diffusion model and associated forward projections of moisture content are found to conform well to experimental results.