It's just plain silly to give hard and fast rules, as only experience will tell you what'll work for you.
Personally, I find tapering too much doesn't work at all for me.
I prepared for my best marathon in this fahion:
- last long run: two weeks before the race
- last speed sessions: 6x1K on the Tuesday before the race, pretty much flat out, but still in control. Then, 40mins tempo run on the Thursday at half-marathon pace
- the day before the race, 30 mins jog, including a K in 2:58
- Total mileage in the last week (not including the race): 60M
As you can see, all these seem to contradict the previous poster's guidelines... Yet 5 previous marathons taught me what would work for me and, with PRs of 15:36 for 5K and 32:10 for 10K, I think I came pretty close to my max ability on the marathon when I ran 2H24...
My philosophy is also, contrary to what most people would suggest, to try and set PRs for 10K, 10M and the half-marathon in the course of my preparation. I am usually in my best shape ever when I prepare for a marathon (as I don't usually train that much), and at lest, if things go badly in the marathon, I'll have other PRs to show for all the hard work.
Just my two pence's worth of advice...