I understand the difficulty of rolling veins, but I still stand behind the never re-registering method for vein care. With rolling veins you can leave the tourniquet on as long as you applied it correctly meaning tight enough for blood to flow in but not out. Also when registering only pull the plunger out slow and minimal and if you register is good then inject at a slower speed, pushing it in too fast will cause it to roll. Also if you applied your tourniquet too tight when you release it after you have registered it can cause the veins to "jump" and can cause a miss.I absolutely must reregister. Absolute must. My veins roll and I can miss an entire 60 unit shot and not feel it til hours later. (I started shooting up when I was overweight) Unless you're skinny, you aren't feeling or seeing that miss. It has saved me so many times.