It can be a bit of a tradeoff between where you want to save time. Kdenlive is a perfectly respectable editor, if you were looking to try out alternatives then you could also try cinelerra or PiTiVi. Kino is useful for simple edits but can quickly get out of its depth.
The problem is that mp4 is a compressed format (hence it fits on the camera smart card), but that makes it harder to edit because your editing program has to do the work of decoding it. What you can do is convert your video file to a raw format like a .dv file or a DV encoded .avi which will make the rendering and editing much faster. The downsides however are that:
- raw video takes up huge amounts of space, expect an hour of SD video to be over 10GB, I don't know how big it will be for HD but its going to be bigger, and some programs don't like editing files that large.
- you have to spend the extra time before and after editing, encoding the files. i.e. turning them from mp4 to raw, editing and then back from raw to mp4.
My main advice would be to try the approach above and play around with other formats, but I don't know how much time you'll actually save. While a 4-5 hour render is quite a while, once you take into account the time to encode at each and the huge increase in disk space needed to work with the files you might decide its not worth it.