I have been using wiper blade inserts to make picks and t-tools. In my experience I have found that not all wiper blade inserts are made with the same quality materials. The best I have come across are Toyoto Echo 2004 wiper blades (from Toyoto, not replacements). The steel in these inserts is excellent. They have wonderful spring and flexibility and more than enough strength to last. My first set of tools made with these are by far the longest lasting I have had. I have a friend who used my tools to get a taste for the sport and he complains about the ones he makes due to the fact that they always break, bend or warp.
As of lately I have been saving the wiper inserts for tension/torque tools and using dewalt bi-metal wood saws-all blades for pick material, I found that they have the same flexibility and endurance of the toyoto steel, but with the additional bonus of being able to craft a handle into the pick design.