Well, thanks. For the voltage regulator I was indicating I couldn't find the symbol for a 7805 in LTspice library.

I'm not real sure your math is correct though. As long as I feed >5V into a 7805 regulator, unless it's overloaded, I should get very close to 5V out. With 4 batteries I'm inputting around 6V so until the batteries discharge somewhat then I should have 5V.

I think the 12F683 will work down to 3.3V so all I'm really buying with the regulator is the time it takes to discharge from 6V to 5V. Which may or may not be significant but for me it is.

If I'm missing something, please let me know.