Ah, I had a look and found that the red motion path is the “past” and green is the “future”.
And I’m assuming that because in this instance the ball is only animating between two locations on the Z axis, that the “past”/red line is overriding the green.
Thus when my ball reaches it’s first keyframe in it’s animation cycle, the motion path is green up until that point. And each cyclical motion path beyond is red no matter which frame I set the end frame to.
This is probably a “by design” question, but why does the “past” motion path override the “future” path if something is animating in a symetrical cycle?