@stfn Cool, I myself learned it from a friend who designs weather stations. The disadvantage is that the timing is not mega precise, in case that's needed.
Also, the ready made tiny boards sold by adafruit become unstable when driving picos (as opposed to arduino boards I supoose), and we had to add 1 Ohm resistors in series to dampen the start up current. Also, we had to pull down the cutoff pin gently to ground for it to reliably wake up again.