Hey Inspector! I have not brewed Rishi's Silver Needle, but I do have a few ounces of their White Peony/Bai Mudan/Whatever you want to call it........anyway, I typically do about 1.5 teaspoons for my 6oz. pot and brew at 160 (F) for 3.5 minutes. I usually do 3 infusions for Rishi's with the second at 185 (F) for 5 minutes and the third at 200 (F) for 7 minutes. I can tell a small degradation in flavor by the end of the third cup. I am sure you could push it to a fourth, maybe even fifth or sixth, but since white peony is a relatively inexpensive tea, compared to Silver Needle, I do not see the need to push it past three. Hope this helps!
-Nick (TaiPing Hou Kui)