Disabling the DAC and other unused timers and clock sources I've gotten the power consumption down from ~12 ma to ~10 ma while active, and to 50-70 ua while in sleep. The voltage divider is in theory taking 15-20 ua, making it toggleable with a mosfet will help with sleep power consumption, but given how much the active state takes, and how long the user is expected to playing it, say 30 minutes a day on average + the samd21 waking up every minute for updating the screen clock, optimizing for the sleep power draw further might not be worth it. (if the device stayed only in sleep mode total battery life is approx. 400+ days) 

Various online power calculators for IoT devices suggest something near 60 days of total battery life with this on/off cycle. I'll have to validate that with experimental data. Reducing sleep current draw by 20u which the voltage divider is theoretically taking provides an additional ~2 days of usage or 3% more runtime.

Active state:

Sleep state: