Recently I have been hearing about Yin Yoga teachers who demand their students go to their final range of motion/deepest edge and stay there, even if sensations are painful or really uncomfortable. This is not my understanding of how to practice Yin Yoga! Pain is never good and being so uncomfortable that you can't stay at the edge makes no sense either. Rather the edge should be played! We approach the edge, then back off and wait for it to move. If it doesn't move, great! Stay...no need to go further. In fact, as the graphic below shows, it is neither important nor essential to be at or close to any final edge. As long as there is some stress on the tissues we get benefit.
This graphic is called the “antifragility curve, and is based on the knowledge that all living beings need stress to regain and maintain optimal health. If there is no stress at all (point A), health is low and the tissues atrophy. However, if there is too much stress (going over the edge past, point B), tissues degenerate and damage occurs. Before this happens, thankfully, the body gives us little warnings in the form of pain. Pain or deep discomfort is a sign to back off. As you can see on the graph, you can happily hang out halfway along this curve (point C) and still gain healthy benefits: you don't have to be near any final edge.
Time is more important than intensity. Go to a place where you feel something but not the most sensation, and then linger longer there, rather that go to the cliff where you won't be able to easily remain. Yin is allowing...if you have to struggle to stay at your edge, you are not practicing Yin Yoga. Do less; achieve more. Cheers!