Recurrence is common and the rate quite variable. This is because the spider veins are there inherently as a result of the pressure difference between the deep veins and the superficial set of veins. Blood flows in the path of least resistance. In the case of spider veins the blood flows from the deep set to the superficial set of veins. So in a typical course of treatments, the veins are destroyed after say 3-5 treatments. Depending on how much pressure difference there is between the deep and superficial set of veins, the spider veins might recur in as soon as one month or after some years.