I own a set of DQ 10's. Bought them from an electrical engineer. They are still 100% original as far as I can tell with the exception of a re-foam He told me they were never driven hard. His wife wasn't too fond of them. They sound fabulous. Crossover looks original with the yellow DQ caps....
How long does it take a decent quality speaker to "wear out"?
After all, they do have moving parts and capacitors. . . .
(I suppose that "decent quality" s a relative term. FTR, I am running a pair of the older B&W 805s, and for all I know, they may not actually meet the criteria of "decent quality.")