In this paper, the long-term stability of the discharge characteristics in a plasma display panel is investigated with the small addition of nitrogen to the conventional Ne-Xe gas mixture. It is found that the characteristics of temporal variation in discharge voltages and full black brightness are enhanced with nitrogen gas addition, which could result in the reduction of miswriting probability and the enhancement of image quality. In the study of the temporal variation of discharge voltages via a Vt close curve, it is observed that nitrogen addition suppresses the changes in discharge voltages. Regarding discharge voltage variation, the change in elements on the surface of the phosphor layer and the temporal modification of the protecting layer are investigated with overfrequency discharge aging using secondary-ion mass spectrometry and a scanning electron microscope, respectively. A small change in elements on the surface of the phosphor layer is observed in the panel, with nitrogen being added to the gas mixture. The reduced ion energy with the addition of nitrogen gas is suggested as a potential reason to induce the different variation of MgO transfer characteristics and discharge voltage.