You are technically only allowed to watch the same number of concurrent streams as the number of discs you have in your plan (1 disc = 1 stream, 2 discs = 2 streams, etc. up to 4 streams).
From the Netflix FAQ:
Some membership plans allow you to watch simultaneously on more than one personal computer or Netflix-ready device. If you are on the Watch Instantly Unlimited plan or the 1-disc-out-at-a-time plan, you may watch only one device at a time. If you are on the 2-discs-out-at-a-time plan, you may watch on up to two devices at a time. Members on the 3-disc plan can watch on up to three devices. The maximum is four devices -- available for members on the 4-or-greater-discs-out-at-a-time plan.
Your account can have up to six unique authorized devices activated (and associated with it) at any given time, including personal computers and Netflix-ready devices. For example, if you're on the 1-disc plan, you can have up to six devices associated with your account, but you can only watch one of them at a time. If you're on the 2-disc plan, you can have up to six devices activated but can only watch two of them at the same time.
Also, you would need a fairly substantial internet connection to have that many streams going concurrently.
Oh, and I thought I would also mention that none of the titles you used in your example are actually currently available on Netflix Watch Instantly.