Our routine once they get the hang of it is 3-5 minutes of fast walk to almost a jog, every other day with day of rest in between. Our treadmill reads at 2-2.5 mph but that may vary in treadmills depending how accurate they are. Our old one seemed to read faster than this one but the belt did slip a bit.
At first we put them in and just get them used to the motion for about 30-60 seconds at very low speed and increase as needed. While the kid is at the front of the lamb, I watch the back legs and control the speed. Then build up to the 3-5 minutes as each lambs coordination allows. We used to track on the off days, but I think we will track and treadmill all on same days with complete rest on off days. Heard that suggestion this spring so we will try it. We haven't messed any up, but we are pretty careful to watch for different behaviors, gait or eating habits.