Sugar, you're missing the point. It is NOT a matter of whether the cable is "air tight". For one thing, it would be next to impossible to achieve without DRASTICALLY raising the cost. Nor does it really matter how tightly the stranding is compacted within the jacket. It is a matter of the materials used as the insulator and the degradation that the JACKET undergoes with time. If you don't believe this, contact Belden or any other manufacturer of cables.
If one has the proper test equipment ( TDR aka Time Domain Reflectometer ), you can also measure the electrical characteristics of cables and compare new samples to old samples. The impedance characteristics, levels of dielectric absorption, velocity factors, etc... of cables DO change over time, albeit very gradually. These rates can be accelerated by exposing the cables to various levels of direct sunlight, fluxuating temperatures, different levels of applied pressure, etc...
Besides that, the originator of the thread made no mention of price range. With that in mind, we all know that a LOT of cables are simply "dressed up" versions of mass produced cables. As such, the "KLH" vs "Mark Levinson" pricing analogy has little to do with "you get what you pay for" i.e. "quality" when it comes to cables.
While one would hope that more expensive cables from a reputable brand made use of better quality materials and had a greater amount of research and development in them than cheaper cables from some generic company, there really is no guarantee of that unless specified as such. Even then, i've seen companies PURPOSELY mis-label products so that they could charge more for them even though they knew that they would not meet spec. Since the average end user would have no way of verifying spec, they get away with it 99% of the time.
Like anything else, let the buyer beware. Sean
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PS... I've bought and used many older cables. So long as they make a good connection and sound good to your ears with no potential for damage to your equipment, i would not worry about it. I was "debating" from a purely technical standpoint.