Hey, that’s a neat challenge. The trick usually starts with the clock: run the MCU at the lowest frequency you can tolerate, and keep the PLL off unless you really need it. Then pull every peripheral to sleep as soon as you’re done – the radio, the ADC, even the GPIOs can cost a few microamps when left idle. Use a low‑drop regulator or a buck‑to‑buck that stops drawing current when the battery voltage dips. And don’t forget the tiny detail: the button you’re using—if it’s a mechanical one, add a pull‑up resistor instead of letting it float; that keeps a microamp’s worth of current from leaking. Finally, think of the power path: place a diode only when you really need isolation, otherwise it’s a silent drain. Keep those tips in mind, and you’ll stretch every milliwatt. Good luck!