Once again, for video there is no specific duration for CD or DVD.
It’s the actual amount of data only that limits the duration. There is no other thing that the actual amount of data that limits the duration of the video (or compressed audio, for that matter) that you can put on a CD or a DVD.
So if one compresses the video a lot, one can put, say, a 4 hours movie onto a single Video CD. I’ve seen this with DivX trasncoding, which can reach very high amounts of compression. A neighbour of mine put all of his movies to CD this way. The thing is, such insane compression ratios end in awful image quality, of course. :Z - suitable only for people with low expectations in terms of image quality, and very small TVs.