The stability of high-pressure xenon gamma-ray specrometers has been measured at Mirmar Sensor. Stability was measured by tracking the <sup>137</sup>Cs peak of the entire spectroscopy system including detector, preamplifier, amplifier, and multichannle analyzer over 6 days in a laboratory setting. Overall system gain drift is about 0.016%. Resolution drifts are about 0.15%. The overall energy resolution is between 1.7 and 1.8% at 662 keV.