In embodiments of adaptive idle timeout for storage devices, a computing device includes a storage device that stores data for read and write access on a rotating media. An operating system of the computing device maintains a device cycle number as an accounting of each time the storage device is powered on-off. The computing device implements a storage device driver that is implemented to obtain the device cycle number of the storage device from the operating system, and determine a projected cycle number over a duration of operational time of the storage device based on the device cycle number. The storage device driver can then determine whether the projected cycle number exceeds a maximum of power on-off cycles within a warranty period of the storage device, and control a frequency of the storage device being powered-off if the projected cycle number exceeds the maximum of power on-off cycles.