Hi Nick & Everyone,
I've been following this post with great interest. Of course I'm finding the low power stuff to be very interesting but equally as important I was discovering what impact my changes have made between the two versions of the library.
Nick: You are using version 1.8 of the library (Keypad2) which had the original problem with shorted pins when pressing multiple keys. Since then I've implemented your suggestions so the latest version, 3.0, includes those fixes.
Zigmund: Along the way I figured out that I could drastically improve the number of times the loop runs per second by restricting the number of calls to the library to once every 10 milliseconds (mS) by default. The default can be changed by setDebounceTime(1) which sets the debounce time to 1mS which is the minimum. By reducing the debounce time it allows getKey() to be called more frequently. I would love to hear how it affects the responsiveness when using version 3.0 of the library. I may need to change my method of limiting.