Well.... That's not the only factor, but what are your thoughts?
Vibrations don't "find paths" over the years. A solid body instrument is essentially (to a first order approximation) a flat plate, albeit with a complex outer perimeter, and has a number of vibrational modes based on frequency. As such there is no path for vibrations to follow as it is frequency dependent and people play different notes at different times. You can (and if you go to YouTube you can see they have done) subjected solid body instruments to swept single frequencies with dust placed on top which, in classic physics lesson fashion, to observe the various vibrational modes. There is some limited academic research out there too but I don't have links to hand.
Given how little the surface of a solid body moves under stimulation from playing bass, the sound of the body itself vibrating will be inaudible. It will absorb some vibrations from the string but it will be mostly turning that to heat rather than acoustic energy. Of the whole system there can be resonant peaks but that's what gives you dead spots and is more likely to be a function of the neck than body.
Vibrational modes might change over time but my understanding is that it would be the wood getting stiffer as it dries out and LESS resonant.