A method is disclosed for programming a patient's stimulator device using an external device. The method obtains information such as a model at the external device, wherein the information is specific to the patient, wherein the information comprises a range or volume of stimulation parameters determined based on testing of the patient that preferably provide sub-perception therapy； and providing from the external device instructions for execution at the stimulator device, the instructions specifying an amplitude, a pulse width, and a frequency of stimulation pulses to be provided at one of more of electrodes in an electrode array of the patient's stimulator device, wherein the instructions vary over time at least one of the amplitude, pulse width, and frequency within the range or volume. Varying at least one of these parameters helps in preventing the patient's neural tissue from become habituated when compared to stimulation that is provided without variance.
