We’re planning to build this into the next version of our new Content Drip extension – http://www.woothemes.com/products/sensei-content-drip/
One alternative way to do this would be using Groups as described in this post – http://www.woothemes.com/2014/02/creating-a-tiered-membership-site-with-sensei-and-groups/
When you create a product that grants access to a Group, it allows you to set a duration, after which the user will be removed from that group.Sambo commented
Likewise - users should not be able to access their course any longer after a period of 12 months. Seems easy enough, how do I get this set up?