I am going to use a MCU + bluetooth BLE module. Its VCC pins are going to connect directly to the terminals of a 3V lithium CR2032 battery, for example a standard 170mAh one. 99% of time the module will stay into deep sleep mode on which the current consumption is <= 1uA, and it will only wake from deep sleep through interrups due level change of the GPIOs. The module work as low as 1.8. The datasheet actually show 0.4uA @ deep sleep.
But there is another SOIC-8 chip on the same board, and it only works with a minimum of 2.5V. My main question is: When the 3V lithium cell reach 2.5V and the second IC start to fail, will I have used a high percentage of the load charge of the CR2032? Maybe used 80% or more of its charge capacity?
EDIT: specs of the module.