> For sure, but how do you know?

In actual engineering, one can work out the theoretical limits (strength, expansion, etc) and measure the current product's performance against the limits. A new widget-making machine or process cannot imbue widgets with physics-defying properties. Any fundamental improvements can only be made on the outside, auch as new alloys; but that would be an entirely different product, nor the one you've been selling for 40 years that your customers trust and love.