Most of our alarm timer and clock are designed with a special feature of endless audible alert with power saving circuit. Thanks for our strictly QC control of power consumption in production line, more than 95% of battery power still remained after the first cycle of 90 days countdown to zero. The original installed battery is possible to last for 10 years without replacing new battery if audible alert is not activated and aging issue is not considered. Therefore, in order to save power for long term running, please try to stop the audible alert as soon as possible after countdown to zero.