[Deke]

If you can tension in the elastic range of the material, you drastically increase the life. I'm not sure i have seen a material or mechanical specification stating the elastic range of surgical tubing, but some testing can go a long ways. One way would be reducing pre tension and adding more tubes, or the tubes may have to be longer depending on the stroke required.

We used steel springs but went through a few iterations to find springs with the correct force and range required in the elastic range. We ruined a number of springs by over stretching into the plastic range of the material.

Our last spring combo made it through two competitions and numerous test shots without any loss off power.