An idle sweep routine for a hard disk drive involves a series of servo-controlled one-Nth (1/N) equivalent sub-band random seeks in one radial direction, followed by another series of servo-controlled one-Nth equivalent sub-band random seeks in the other radial direction, where a complete band refers to the complete set of user-data tracks and a one-Nth sub-band refers to a contiguous 1/N portion of the complete band. For example, a first series of ⅕ sub-band random seeks may be in the disk outer diameter (OD) to inner diameter (ID) direction, followed by a second set of ⅕ sub-band random seeks in the ID to OD direction. Based on disk scratch and Si smear robustness, ⅕ sub-band random seeks are found effective in moving the sider over a significant number of tracks during each seek to likely inhibit disk lubrication degradation and avoid thermal asperities during such an idle sweep routine.