DLR Battery Save Mode

Does anyone know what the “battery save mode” on the DLR does??

The software help says tha t “Battery Save Allows the user to enable or disable battery save mode. Disabling this feature causes the battery life to shorten by about 20%. The default setting is on.”

OK, so it makes the battery last longer. There must be a downside or we would not have been given the option to enable/disable.