A data logging system that utilizes a schedule of data transfer periods for transferring data from devices to a server. A communication of an actual data transfer size of stored data in a first device of the devices is obtained by the server from the first device. A corresponding future data transfer size of the stored data is estimated by the server, based on a historic data transfer size for data previously transferred from the first device to the server. The schedule is currently based on the historic data transfer size for the first device. The server updates the schedule if the server has determined that a difference exists between the actual data transfer size and the corresponding estimated future data transfer size. A transmission from the first device of the data actually stored in the first device is received by the server in accordance with the schedule.