Personally, the peace of mind that things will be handled when something goes wrong is worth the extra $50 for two additional years. Thats just $2.50 a week, even if nothing were fixed.
When they fixed my hard drive, they installed the OS and I restored my data from time machine and I was back in business.
Figure out what your time is worth after taxes and then figure out how much time you would spend just trying to assess what the best course is to handle a problem. That cost is gone when you can just hand it to Apple and they return it to you whole.