NiO-based resistive-switching memory (RRAM) is a promising new technology for high-density nonvolatile storage. The main obstacles to practical application are the large and hardly scalable reset (programming) current and the reliability at high temperature. This letter studies temperature-accelerated data retention in RRAM cells from both experimental and theoretical standpoints, addressing the size/nature of the conductive filament and clarifying the tradeoff between data retention and reset current.