In Agile, you are supposed to ship product on a regular cadence. All features are added to a product backlog, divided into small projects that fit within a sprint, and then prioritized. The backlog is just a way to keep track of all of the ideas people have, requests from customers, major bugs and other things.
The first patent for Pristiq is set to expire in February 2022. This is the earliest predictable date that a generic version of the drug could become available. However, other circumstances could come up to extend or shorten the exclusivity period.
The first patent for Crestor currently expires in January 2016. This is the earliest possible date that a generic version could become available. However, there are other circumstances that could come up to extend the exclusivity period of the medication beyond 2016.