Short Answer – No
The term stretch is actually wrong, most bowstring material cannot stretch “it will elongate” meaning it has somewhat of an elasticity to it but will always return to same point.  What most perceive as stretch is actually small imperfections in the raw fiber “little twists” from the manufacturing process of the fiber along with the build quality of the bowstring itself.  Here at A3 we remove those imperfections prior to building the bowstring and then we take it another step further and utilize our precycle technology to assure your bowstrings will never move “or stretch”
We have actually taken other manufacturers bowstrings, checked the lengths, ran them through our Pre-Cycle Process and have seen over 1/4″ of growth in the string.