A display device including a display panel with a plurality of panel blocks, and further including a screen saver controller, the controller comprising: a load calculator configured to generate load data of each of the plurality of panel blocks (110, 120) included in the display panel based on input image data, wherein the load data of a given panel block is calculated from an average intensity of intensities of the pixels in the given panel block, or the load data is generated from an average voltage of data voltages applied to the pixels of the given panel block; a life calculator configured to generate life data of each of the panel blocks, wherein the life data of a given panel block is a sum of deterioration stress values accumulated in the given panel block, wherein the life data of the given panel block increases as an accumulated usage amount of the given panel block increases; a first logic circuit configured to receive the load data and the life data, and to generate gain data based on the load data and the life data; and a second logic circuit configured to receive the input image data and the gain data, and to generate screen saver data based on the input image data and the gain data, wherein the display device is configured to operate in a screen saver mode in response to determining, based on the input image data, that an image displayed on the display panel is a still image, and the screen saver controller is configured to adjust a luminance of the display panel based on the screen saver data in response to the display device operating in the screen saver mode for performing a screen saver operation, such to maintain for a first period a luminance of the display panel until a start time of the screen saver operation, and to perform the screen saver operation starting at the start time, wherein the screen saver operation includes gradually decreasing, for a second period, the luminance of the display panel until it reaches a set minimum luminance, and maintaining the minimum luminance for a third period; wherein the gain data includes start time gain data for adjusting the start time of the screen saver operation based on the load data and the life data, wherein the first logic circuit is configured to generate the start time gain data such to control the start time of the screen saver operation to start earlier as an average value of the load data of the panel blocks increases and wherein the first logic circuit is configured to generate the start time gain data such to control the start time of the screen saver operation to start earlier as an average value of the life data of the panel blocks increases. a load calculator configured to generate load data of each of the plurality of panel blocks (110, 120) included in the display panel based on input image data, wherein the load data of a given panel block is calculated from an average intensity of intensities of the pixels in the given panel block, or the load data is generated from an average voltage of data voltages applied to the pixels of the given panel block; a life calculator configured to generate life data of each of the panel blocks, wherein the life data of a given panel block is a sum of deterioration stress values accumulated in the given panel block, wherein the life data of the given panel block increases as an accumulated usage amount of the given panel block increases; a first logic circuit configured to receive the load data and the life data, and to generate gain data based on the load data and the life data; and a second logic circuit configured to receive the input image data and the gain data, and to generate screen saver data based on the input image data and the gain data, wherein the display device is configured to operate in a screen saver mode in response to determining, based on the input image data, that an image displayed on the display panel is a still image, and the screen saver controller is configured to adjust a luminance of the display panel based on the screen saver data in response to the display device operating in the screen saver mode for performing a screen saver operation, such to maintain for a first period a luminance of the display panel until a start time of the screen saver operation, and to perform the screen saver operation starting at the start time, wherein the screen saver operation includes gradually decreasing, for a second period, the luminance of the display panel until it reaches a set minimum luminance, and maintaining the minimum luminance for a third period; wherein the gain data includes start time gain data for adjusting the start time of the screen saver operation based on the load data and the life data, wherein the first logic circuit is configured to generate the start time gain data such to control the start time of the screen saver operation to start earlier as an average value of the load data of the panel blocks increases and wherein the first logic circuit is configured to generate the start time gain data such to control the start time of the screen saver operation to start earlier as an average value of the life data of the panel blocks increases.