Bottom of the page on MSNDirect.com...
Guaranteed until at least January 1, 2014. You have a while, and by then, you may possibly be looking to upgrade systems anyway. And I think that's the idea.
Also, as far as I can see, you can't just buy the service directly from MSN... you HAVE to buy it from Amazon or Best Buy, which blows since they're both $130, instead of MSN's advertised price of $99.