A lot depends on the bow itself as well as the method in which the string is made. Many of the old bows did not have properly reinforced tips using phenolic that help reduce the stress on the tips. Perfectly shaped angles in the string notches also dissipates these pressures as well. Same with front of limb facing archer many old bows had string notches that were filed all the way through the glass to core wood, a weak spot with modern strings.
With that said I personally shoot bows from the sixties that have been reworked to allow the use of a padded FF string without hesitation, the bow feels better, quieter, and feels less stressed with the modern string. Same bow oscillated for several seconds after the shot with B55 which had the feeling of inducing more stress on the bow. Another issue on older bows was the glass used which was unidirectional and cracked over time do to expansion and contraction of core wood leaving tiny cracks running along the limbs length.
If you value the bow more than just a tool than the use of FF may not be the best bet!
May find this interesting:
http://www.tradarcher.com/string_poll.html