Fedora already supports releases for 12 months, as the most recent 2 releases are supported. Fedora 19 has been out for six months, and will be supported for a further six (or so!) months until Fedora 21 is released. In contrast, Ubuntu only supports its releases for 9 months, except for the LTS releases.

You still need to subdivide the image for motion estimation, as some parts of a moving image move at different rates to others. Subdividing into blocks gives you O(N) complexity in the size of the input image, whereas doing a DCT transformation has O(N log N) complexity.