The biggest concerns will probably be resources/bandwidth, for example, you'll be pulling the large video files across the network so connection speed and server disk IOPS will be factors.

I believe there will also be a few different things at play depending on whether you use the desktop client or the web client.

Another thing is properly managing your volumes (definitely use logical volumes so you can break everything into chunks, and split them across multiple drives as needed).

However, all-in-all it shouldn't be too much of a problem. Our repository is over 25TB, no video (yet), but we do have some documents that are several thousand pages in color (some as large as 3GB).

The overall size of your repository doesn't sound like it will be an issue. The more important thing will almost certainly end up being the size of the individual files, so I would start testing that first to try and identify your potential bottlenecks.

Long term planning for flash storage might be a good idea too. When we switched to flash storage for the volumes we saw a huge improvement in document retrieval times.