I still find it a bit odd that the 3-day week before I go on vacation is probably my most productive, focused week. It probably has to do with focus and weeding out the distractions with the "I need to get this done by Weds night, so can we talk when I get back?".

I've worked a sustained 60 for a lot of years and done back-to-back 80's. I just don't think I was super productive. My most personally productive run was on a job that I had 4 hours in the morning to program and was doing something completely different in the afternoon.