Ranger Steve, I think what you mean is that older saws are better for the job because they were ground thinner in the first place,thereby being inherently more flexible, and quite possibly the composition of the steel used contributes to a better sound than that used in modern saws. Also, just as in guitars, it is the better quality tools which survive.

Continued use does not make a handsaw "flexible", leastways not in my experience.

Murray