There is a lot to think of......

But my very first program works just fine now!

One LED blinks every second and goes on continously after 9 minutes.
Another LED goes on when the voltage drops below 2.5 Volts....

B.t.w. I understand that there is a calibration factor inside each PIC that shall/could be used to get better clock accuracy.
Is the PBP using this automatically?
My 9 minute timer is accurate within 1 second (two different PICs) just as it is.