The speakers holding up really depends more on the cabinet they're installed in and what your expectations of them are. Older speakers meant for sealed cabinets have relatively short excursion and lower power handling, but are far more efficient across the board, including low frequencies. (Additionally, as speakers age, their suspension loosens and their resonant fequency drops.) Modern speakers designed for ported cabs have tremendous amounts of power handling and excursion, but are more inefficient and less responsive. The tradeoff is supposed to be for additional power handling for additional volume, but that's rarely true, and if you're installing vintage speakers in a modern or homebrew ported cabinet hit with large amounts of s/s power, you're already asking for trouble. It's not the fault of the speakers.
