Age Limit for Speaker Cables

I have a 8' pair of XLR Series 5 reference speaker cables purchased new in 1997. No oxidation or cracking found in the cables and everything seems fine. Throughout the years I've upgraded all other components (many times) and cables except these. My other equipment is currently under 2 years old.
My budget is $1000 and am wondering if today's cables are that much more improved than in 1997. Can I find a better, more transparent, accurate, musical sounding cable for less than what I paid during the Clinton presidency? Much less?
Thanks and happy listening
Look on the cable it should have a expiration date on it.
Mapleshade has a 30 return policy if you don't like what you hear.
I, myself, had the original Helix and recently upgraded to the Double Helix and couldn't be happier. A big step up.

Good luck in your search as your budget allows you a lot of choices.

All the best,
Post removed 
Sometimes cables can oxidize as Elizabeth mentioned about the Monster Cables above. Cables usually become obslete to the listener due to a system change. I have setttled on DNM speaker cables and IC's. DNM has been around for quite some time and has stayed with the same geometry since inception. They use a solid core copper cable and have two types. Precision is for speakers that are >90db and Stereo for speakers that are <90db efficiency.
They will run way less than your 1k budget.
I guess this only proves that all good cables, like many other things in life, must someday come to an end! I think oxidation is the primary problem and then there is possible fraying of the actual cover. In the end though, a good cable should probably last you quite a while.
Anyone know if Nordost cables suffer from the same sort of problems? Been thinking of giving their cables a try in my system...