Multiple power adaptor failures

I'm posting on here partly out of frustration, and partly in the hope that someone may be able to help.

I have a late 2011 MacBook Pro 13 inch, that up until July of this year (2013), I was very happy with.

However, in July my power adaptor failed. I had a dimly lit LED and when clicking the battery icon, I was told "Battery is not charging", "Power source: Power Adaptor".

I took my MacBook to the local Premium Reseller (on apples advice) and they replaced the adaptor.

The problem re-occured only a month later. Same problem, same advice, same replacement. This happened THREE times, each time about a month since the previous occasion.

These adaptors were treated well. Rarely used in a different location, and kept free of kinks or stresses.

This month, the problem repeated, AGAIN. I took it to my local service centre and this time they diagnosed a logic board failure, and replaced the part under applecare. They also provided ANOTHER new adaptor.

I picked up my MacBook yesterday. The problem repeated itself today.

I am starting to go slightly mad at this point. The most apple will help over the phone is to tell me to visit the repair centre again and hope for the best, but I'm at my wits end now.

If anyone has any idea what the problem could be, please let me know, because I'm really getting nowhere at the moment with applecare.