Do stores allow you to extend a service plan?

[erehwon]

I got my xbox360 from walmart a couple years ago with a service plan. I think my plan might be expiring this year. Do they let you extend the plan? On most products, I wouldn't consider this, but the xbox360 is different. $20 for another 2 years is probably worth it in my opinion. I'm lucky that I've only had to send it in once.

Edit: Found the answer to my own question.