I am using the radio power modes and I do put the radio to sleep as well.
I checked the tutorial you sent, but is there any easier way to control the power delivery to the sensors without a separate watchdog board?
Also I apologize the lack of clarity - I guess the one that's hard to read in the diagram is the D18B20 sensor.
And thanks for the clarifications on the voltage regulator. I will quickly get rid of it.