Have you tried:
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.
Temporary work-around with Product Bundles (WooCommerce premium add-on). You can add the same course to multiple Product Bundles. Learner pays for a specific Product Bundle, and has access to all courses within that Bundle.
You may need to add at least 2 courses to create a "bundle".