This paper investigates the changes in the surface and discharge characteristics during long-term (1000-hour) discharge in microdischarge cells with MgO crystal powders as a parameter of the MgO thickness variation. For four different MgO thicknesses (2500, 3500, 4500, and 5500 angstrom), the changes in the MgO surfaces were monitored by the SEM, and X-ray diffraction (XRD), and the resultant changes in the discharge characteristics such as the firing voltage and address delay time were also examined during the long-term (1000-hour) discharge. When increasing the MgO thickness ranging from 2500 to 5500 angstrom, it was observed that the grain size increased and (111) peak was intensified. Also, after 1000-hour discharge, it was observed that the firing voltage increased slightly with an increase in the MgO thickness, whereas the address discharge delay decreased with an increase in the MgO thickness.