My experience: I'm 52 years old. My 1st spider vein injections started at age 21 I was so young and wouldn't even shorts--Fantastic results -(out came the shorts and bathing suits) - then, about every 7 years (maintenance (diff. doctors) changes, locations, etc. Throughout the years the results have been different. It mostly depends on the doctor / experience / and type of solution used is very important, as I have discovered on my own. Keep a diary so you can refer back to type of solution that best works for you. For whatever reasons as the years pass your doctors and solution type will change. Now, for the main vein (valve) backflow, whatever, at age 50, I was told the same thing. Insurance paid (I had 1 backflow maybe 2 veins in just 1 leg) My spider veins were kept under control throughout the years by going every 5 - 7 years and having just (1) session of injections that included both legs. After being told that I needed vein ablation (to prevent and even improve the others) and the bonus was that insurance paid. Well, the worst results ever! I had my leg threaded (vein heated) followed by a few injections and within a year found myself getting vein injections again. Still poor results. It's in the solution. I am sorry to say that I didn't keep that diary throughout the years. But, I can tell you that my worst (no results) on my last 2 vein injections (the injections that followed the Heated Vein ablation) and the following year (injection only by another doctor and clinic) used the same solution (Sodium tetradecyl Sulfate) I know this now because I am getting ready to try again and I was able to track the solution name down from the last 2 sources used recently. (Bad results if no results at all) Sodium tetradecly Sulfate did not work for me. --- I wish I knew what the Doctor used back in the 80's when the results were fantastic.(1 - visit) And all of the other vein injections that followed through the years up until 2001, worked pretty good with 1 visit. I feel if you get good results (80% would be considered good) and then maintain every 5 - 7 years using the same solution type with a good experienced doctor, you will be happy you kept a diary.