As I think you already know 1000Hz is the only frequency that supposedly stimulates the acupuncture points directly but I feel from my experience that 50Hz can also be used to stimulate such points as the Jing-River and He-Sea points as well. Therefore I would use 1000Hz only to stimulate peripheral acupuncture points on the extremities and 1000Hz or 50Hz to stimulate points near the centre of the body. Generally a needle is retained for a longer period of time in order to stimulate/nourish so I would recommend 1-2mins per point to stimulate and 30seconds per point to disperse.
coMra Practitioner, South Africa