I've owned couple of Macbook and Macbook pros since 2009 and never had any issue with the fraying, but I've seen one case of fraying from a friend's Macbook Pro

I've owned couple of Macbook and Macbook pros since 2009 and never had any issue with the fraying, but I've seen one case of fraying from a friend's Macbook Pro just few months ago. I didn't think she'd abused her adapter in anyway. On a side note, I had every single original iPhone charging cable fray after less than couple of years of use (including 30pin and lightning cables from iPhone 3, 3G, iPhone 4, and my current iPhone 6). It is very annoying. A good way to fix is to use Suguru (https://sugru.com/how-to/fix-a-broken-cable https://sugru.com/how-to/fix-a-broken-cable), which seems to be made to fix things like this, and stronger than heat-shrink tubing.