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Due to improved technology terrestrial laser scanners (TLS) are increasingly used for tasks demanding high accuracy, such as deformation monitoring. Within this field, often long-term measurements are acquired, for which the temporal stability of the laser scanner’s observations need to be assured or at least its magnitude and influence factors should be known. While these influence factors have been investigated for most of the geo-sensors taking part in long-term monitoring, it has not been investigated for TLS yet. In this study, we empirically reveal the stability of terrestrial laser scanner observations at long-term measurements. With these investigations, we can analyze the drifts, which occur in the polar observations during the warm-up phase and after it. It is shown that the drifts cause both rigid body movements and inner shape deformations of the point cloud. By re-stationing the scanner during long-term measurements, the drifts in the vertical angle in particular can be reduced by half.