I am thinking of buying some used speakers that are about 5 years old. I am not talking about blowing speakers out, but how many years it would take them to age to the point where the sound would be degraded. I have have heard about surrounds becoming dry and cracking, but this is like after 20 years. I have noticed that speakers depreciate quite a bit if they're only a few years old, like a previous model, and you can pick them up for a lot less.