Keeping Drivers Healthy

I own Audio Physic Tempo IIIs. The originals, without the grills. Wonderful speakers; I want to keep them that way. No grills plus the slanted front results in dust accumulating on the top of the midrange/woofers. I occasionally dust them, but I wonder if there is something more effective to do. Any suggestions? Will most driver surrounds eventually dry out and become less flexible? Can they be wiped with something that will maintain optimal flexibility without harming them acoustically?