I've owned various MBP's and Airs since they switched to Intel processors (whenever that was). I travel heavily, and port my laptops between the office and two houses when I'm not traveling. I don't recall any problems with any of my power adapters ever, other than 1 which apparently just up and quit one day. I have a couple of MagSafe adapters that are 6+ years old and going strong.
Are there really no cracks in the cord around where it enters the adapter or where it connects to the magsafe? No brown or yellow plastic?
Up until about 6 months ago it was my main computer, used constantly and taken everywhere. It's the original PS too. Maybe the way I wind up the cords has something to do with it? Most people I see don't do it this way: [1]
[0] -- http://i.imgur.com/IxlZPWH.jpg [1] -- http://i.imgur.com/TEzfDx4.jpg