I never draw for longer than 10 seconds. Learned a long time ago while doing isometric and or weight training, that lactic acid build-up in muscles can cause muscle quivering etc. No matter how good condition you have all your muscle groups it is a physiological phenomenon that is a fact of life. Any hold longer is certainly possible but the internal changes within our muscle groups cause muscle fatigue, hence, quivering, and lack of fine control. Just when you need that fine control you have unknowingly lost your edge. Tragically, many times the results are wounded game, long tracking, and quite freguently lost game. As a test for this phenomenon just squeeze a fist tightly for 10 seconds. Release that tight squeeze and you will notice a calming feeling in your hand. That is the muscle group recovering from lactic acid build-up. I urge you to try and keep your draws to a minimum hold time. JMO, but I believe you will have more success and fewer errors at release.