Just recently did a Strkes & Spares stencil respray.
We got caught with an OLD stock VINYL stencil set.
The vinyl was terribly stretchy and the adhesion between the actual stencil material and its backing was way too high.
Needless to say, this caused headaches with distortion during application and rendered the stencils unfit for re-use.
My research tells me the current generation of stencil sets are polyethylene which obviates these hassles.
Just so you know what to avoid.