Additive manufacturing as an emerging technique, however, delivers relatively low reliability compared to traditional manufacturing. Unlike in traditional manufacturing systems that manufacturers mainly focus on the machine reliability by adopting failure rates of equipment, in additive manufacturing systems the performance of reliability is often evaluated by the consistency of measurement results. In addition, the reliability of additive manufacturing systems is not only affected by the failure rates of machine elements, the condition of the photo-sensitive raw material could also lead to variations on the overall performance of the additive-manufactured products and thus affect the reliability. In this work, the impact of raw material condition with respect to the material aging time on the reliability of the stereolithography manufactured products is evaluated experimentally. More specifically, the liquid resin is sampled and stored in a laboratory environment for 2, 6, 8, and 12 days of aging, respectively. A series of specimens are printed with the aged raw materials as well as the fresh raw material. By computing the standard deviation and correlation of the measurements among specimens, the results indicate that material aging time has a negligible impact on the geometric dimension of the specimens while it does significantly affect the hardness. In other words, the results of the work imply that the reliability of stereolithography is significantly affected by raw material aging time.