Today I replaced the Deek Robot Pro Mini clone by an original Sprakfun one. Although the clone worked quite well I could not manage to cut the traces right to preserve power for this battery powered Arduino. In an attempt to disable the onboard power regulator and LED I wasted two. The nice thing about the latest version of the Sparkfun Arduino Pro Mini 328 (3.3V/8MHz) is that it comes with a desolder mod that will disable the on board LED and power regulator. Have a look at the uploaded image.
When the on board power regulator is disabled you have to power it with regulated 3.3v, so disable the VCC pin on the FTDI header.
As soon as it runs steady for a couple of days I will try to add the following battery measurement adjustment described on the MySensors battery powered sensors page. And I will give my Multimeter a try on the current power usage. So more on this topic later.