yes it is about the riding.
but,
a video that has a little thought gone into the editing/music is more enjoyable to watch and will get watched more often.
plus when i make a video i am making something for me/my friends and i want to be able to look back and enjoy watching it, a bit of pride in what you make never hurt anyone.
a lot of the time its just simple things, like i have seen vids that have had a huge drop gap in a mellow part of the song and a smally techy line in a screamy bit, swap them around and the video is instantly better. when i am making a vid i NEVER use the first song i think will work.
as for time i agree with wayne 2-3mins is long enough for one rider and maybe 4-7 for a group of riders, and whatever for bigger events, roadtrip, bikeshows, etc etc
mike