In a printing machine having at least one transfer device driven in response to an electrical signal and operable to transfer a medium onto a sheet, a method of controlling the magnitude of the electrical signal driving the transfer device comprises assigning a magnitude of the electrical signal for driving the transfer device to each of at least two transfer stress conditions, evaluating at least one operating parameter of the printing machine relative to a corresponding pre-determined threshold value, selecting one of the at least two transfer stress conditions based on the evaluation of the at least one operating parameter, and applying the magnitude of the electrical signal corresponding to the selected stress condition to the electrically-driven transfer device. The operating parameters may include environmental parameters, such as altitude and humidity, sheet properties, such as paper weight, and machine parameters, such as transfer device life.