longevity of good speakers

i am somewhat new at the audiophile game and i am looking for some advice on speakers. NOT SUGGESTIONS. my question is in buying a high caliber speaker like the verity ovations on the used market, with average play, approx. 20 hrs./week, how long can they be expected to play at their top form? in other words, if i buy a six year old set of good speakers, how long could i realistically expect them to give me great satisfaction?