SmashedLife discovered that Netflix is testing unlimited Watch Instantly hours with new customers. Unfortunately, "unlimited hours" only seems to be available for new subscribers at this time:
I called up the Instant Watch support line and asked to get unlimited hours but they told me it was some kind of promotion and it was to new members only. I hope they roll it out to everyone because they seems to really have picked up the movies and TV shows on there such as Heroes.
To see this offer, you have to log out of your Netflix account, clear cookies, click on "How it Works," and "Click here to learn about other available plans."
Netflix currently offers more than 5,000 movies and TV episodes on the Watch Instantly feature.