I'm guessing you don't use your laptop in your lap. It is impossible to avoid some strain on the cable while the computer is on your lap, because it must hang unsupported.
Use it this way for a while and I guarantee that no matter how much you care, the plastic will splinter exposing the inner cables and eventually shorting them.
I do use my computer in my lap; the strain is minimal and has no real effect on durability. That's like a couple of ounces of weight–there's no no way that will permanently damage the cable.
There should be no way, but as plenty of people can attest to... it happens. Really, why would so many people be complaining if it wasn't true?
I'm still using my late 2011 machine as a daily driver, day in and day out. I think you can agree I don't generally mistreat my stuff (or the thing would be destroyed already). I'm telling you I've been careful with the charger cables, and still got 3 of them to fry this way.
You may or may not believe me, but at least you should understand that my opinion (and many others') is that those cable strains are unfit for their purpose.
Use it this way for a while and I guarantee that no matter how much you care, the plastic will splinter exposing the inner cables and eventually shorting them.