I´ve got up to 48 hours from a dual 18650 5000mAh battery pack - sketch is always connected to wifi with a status led and sending a simple UDP string when a button is pressed maybe 10 times per day. 48 hours is acceptable for me. I´ve had to use a TP4056 for the charging as the MKR1000 isn´t up to the job of charging a 5000mAh battery pack in one sitting.