Per your comment... speed workouts are pretty common for marathon training- and in fact many of our workouts are adaptations from those espoused by Hansons':
General marathon link: http://runningtimes.com/rt/articles/?id=4447&page=1&c=83
speed sessions: http://runningtimes.com/rt/articles/?id=4420&page=1&c=83
Also, we're not exclusively marathoners- before boston we're racing a 5k, 10k, 8k, and jake's doing a 10 miler... so we need some speed.. so three miles just under 10k pace 4:55-4:45 and the 800s were for the shorter races we have coming up.
And yes, we will be doing tempo runs in late feb/early march. Last year this involved 12 miles at 5:40s then dropping into 5:30s.