I completely agree with you Sean and others. It is just my opinion that the typical generic "clear" jacket cable is so poorly made, it is going bad the minute is leaves the factory. I would not recommend it brand new, so used is a non starter. On the other end of the spectrum, I have re-terminated older high quality cable. When I cut the ends off and stripped down some of the covering, the copper cable under there was as shinny as new.
Quality cables is a recent event. Most cable brands out there are less than five to seven years old. I would not consider any of them old yet. Some of the very oldest MIT music hose from 1985 may be a risk, but has anyone cut then open or tested them to see? The MIT Terminator series only started in 1994 (white jacket); the ones with the grey jacket are only a couple years old at the most.
The original poster did not specify copper cable. Silver cable is another story completely. As well as silver/copper strands like Nordost and others; and gold/silver cable like Siltech. These types of cable should last a lot longer than copper. It is my understanding that silver is still a good conductor when it tarnishes. Gold's conducting properties will be the same a million years from now.