I've had two of those cords for over 2 years with no prolems, cablesneed to be treated with care, careful winding, and most importanly, do no stress either end. (twisting, pulling, etc.).
Carefully coil your cable in a neat circle with out twisting it all up. Also I have 3 of the original magsafe connectors that still work perfectly, due to careful and correct coiling, if you don't know coiling techiques, have someone who knows cables show you. They should show you at an Apple store.(I would think for no charge)
It's amazing that Apple has to explain proper care of things like power adapters, but they do:
This applies to anything with a power cord.
I have PowerBook G4 adapters that are over a decade old. They were all in heavy use involving frequent travel. None ever frayed and they all work fine to this day.
Take care of them and they last. All you need is a little bit of common sense.