Read about any thread from before the launch of the new MBPs (14th of October).
The GPU used in the last gen MBPs (The one you bought), has a design flaw which makes it overheat and fail in the long run. It's still unclear if they all suffer from the problem but more and more people's MBPs fail after 1 year or so.
Apple has upped the warranty for the GPU from 1 year to 2 years but people with Applecare still only get 3 years total.
I'm not too technical on this but search for the name of the GPU in the forum and you will get plenty information.
Sorry to make you stress about this but you better stay informed than stay oblivious.