I've now run the experiment and got part of my answer.
I am trying to see how long a single 3.2v lifepo battery will last on a Lolin 32 lite. To save battery, i put the esp32 into deep sleep every 12 seconds after writing sensor values to an array. After 120 seconds the sensor values are averaged and saved to SPIFFS, and it goes to sleep again.
By commenting out the Serial.begin and Serial.print lines, it saves 30% of the time it is awake.
I assume that this will extend battery life.