Every Macbook that's entered my house over the last ~6 years (4 work, 2 personal) has had its adapter abused horribly, and none of them have frayed. Meanwhile they've saved all of them from multiple rapidly-getting-friendly-with-the-floor events (kids).

One thing I don't do is wrap the Magsafe end around those little prongs when I pack it. I just bunch it up roughly and toss it in the bag. Maybe that's what frays it?