Normally I procrastinate, with contest deadlines (usually Tekko, Sakura-Con and, until this year, Anime Evolution) being the goad to get me off my butt and get videos finished.
That being said, this year I seem to be on a bit of a roll (had two videos sort of hit my head, edit themselves there pretty swiftly and then took less than a week to bang out IRL), so I've decided to see if I can sustain that and crank out a video a month for the foreseeable future.
Generally, the way I edit is that I get the thing done in my head first and then sit down and go hell for leather around work hours until it's finished. Of course, this year I was also trying to be responsible because with the Sakura-Con deadline at the end of the month and Dragon Age 2 coming out tomorrow, I knew if I didn't get them done before today, there was a good chance they wouldn't get done.
So, I guess to answer your question---I don't really edit until brain says it's time to, and then I don't do anything else at home but edit until the video's done. Which, the way I work, is generally 3 days to about a week or so from start to finish.