The durability associated with how 'narrow' or thin the arrow pass is depends on several other factors.... The integrity of the material and any glue joints, degree of any grain runnout, whether it is one piece or several pieces laminated together, specific design/shape characteristics, the draw weight, and the big one... how deep it is front to back.
If, in the design, material is removed from the width, but added to the depth in that same area, it may actually be stronger.... that is until it gets thin enough lose stability.
What are the dimensions and models of the bows you're concerned about? How wide side to side, how deep front to back, draw weight, etc? Got any pictures?