We present the repeatability performance of an automated non-contact probe system for on-wafer device and integrated circuit characterization in the 500-750 GHz band. Unlike conventional contact-probe systems, a computer controlled x-y translation stage is employed to realize a completely automated non-contact probe setup. Thanks to this simplicity, far superior repeatability performance can be achieved with great ease. We present the repeatability study specifically for the 500-750 GHz band utilizing a precision servo system with 1 micron translation accuracy. At 625 GHz, our setup achieves 2.2° deviation in phase and 4.4% deviation in magnitude for 25 successive measurements spanning over 1.5 hours. This fully computerized non-contact probe system also facilitates intermittent re-calibrations that are normally needed for reliable sub-mmW measurements.