Sure, you can see which Watch Instantly movies are expiring when you check your queue on the Netflix website. But now that my DVD queue is on autopilot and I only stream videos from my Roku box, I don't get around to visiting the Netflix site all that often. But I do check my Twitter alot, so I'm thankful Queuenoodle is around to tell me when movies are set to expire. [Queuenoodle]
Im surprised at all the comments from people who didnt know streaming movies "expire" on Netflix.
When a movie is about to expire, they let you know by telling you the date its available to (the date usually appears a month or so before the expiration occurs). If theres no date its not near expiring, and once a movie/show expires, if it was in your instant list it gets saved to your instant wish list thing so itll pop back into your instant queue the next time its available (Ive already had this happen with several movies).
Depending on how you watch your streamed movies (if its on the website, see above) I assume will depend on whether/how youre notified of expiration dates, but I know using the xbox and PS3 you get the expiration dates.