For lack of a better description, I am calling it the 4 Week Push. "It" is a key period of time starting 6 weeks before your scheduled marathon ending 2 weeks before.
We all know that unless you are a professional runner or retired, marathon training never goes as well as we'd like. Work, family obligations, and vacations often interfere, and while missing one or two workouts may not be a big deal over 10-12 weeks, I think it might over 4 weeks.
If possible, I highly encourage runners to take this 4 week stretch before your marathon very seriously. This is the time to put aside other distractions and give your workouts a higher priority. Don't schedule any trips, unless of course it frees up your time. Focus on those 3 key workouts- the long run, the interval, and the tempo. Get your rest, eat right, and give those workouts your best effort.
When I turned 40, I stumbled onto this by accident. While I had been doing my 16-17 mile runs on the weekend, I upped a second 10-12 miler to 16-17, so did 2 of those 48 hours apart over a 4 week span leading up to my marathons. It worked beautifully, as I was able to break 2 hr 40 minutes in 5 different races, never running further than 18 miles in a workout.
Too often I've seen runners put in weeks of training, only to sabotage their work by losing their edge in the last month. Don't let it happen.
(c) Dave Elger 2008 All rights reserved