From Ling Shu, chapter one:
“When people contract a disease in their five viscera, it is like having a thorn embedded in the body, like being tarnished, like being tied into a knot, like being closed down. The thorn although embedded for a long time, can be removed; the tarnish although present for a long time, can be wiped clean; the knot although tied for quite a long time, can be untied; what was closed down can be opened again. To say that a chronic disease is not curable is speaking incorrectly. The doctor that is good at acupuncture can find the disease, can remove the thorn, can wipe away the tarnished, can untie the knot, and open the closed. A disease, although chronic, can be overcome. Those who say that diseases are incurable, have not mastered the art of acupuncture.”
The Nei Jing also contains methods of diagnosing terminal diseases. It does not claim that everyone will live forever by using acupuncture. The point here, is that it is always helpful to seek acupuncture treatment regardless of the illness.