If my figure's starting pose is close to a zero pose then I might start the pose at frame 21 or even 11. But for extreme changes in starting position I use 31. Also, I duplicate the frame 31 keyframes at frame 30 and convert both sets of keyframes to spline break. I've gotten animations longer than 1000 frames to work well this way. The key is well-designed dynamic clothing so you don't get the dreaded "Cloth Simulation Failed at Frame XX"