This project requires ultra low power consumption while sleeping, and it won't have the option to switch off either the temperature sensor or the memory chip through their voltage regulator, as all devices will be powered directly by the 3V battery.

The MCU's power consumption while on power-save with a Real Time Counter running is 1.3uA, and the MAX30205 shutdown-mode power consumption at 3.0V and around 30°C is 1.62uA. The memory chip consumes 350nA on deep power down mode. This brings the total power consumption to 3.22uA while inactive. On a CR2032, which usually has over 200mA capacity, this logger could, in theory, sleep for over seven years.

Of course I'll have to consider the high consumption for the few milliseconds it takes for the chips to wake up, sense and store temperature, and go back to sleep, and also the battery's self-discharge. But I'm fairly confident that even with bulk-purchased coin cells, which often have a lower capacity, the target of 180 days is achievable.