Don't know what you should do, necessarily, but I'll tell you what I did. Hopefully some of those more educated in the science of things will add their two cents (three cents Canadian).
First you need to know I've never followed any specific training methods, or applied any scientific theories to improve my running. I run for me, and for the feeling I get from it. Every run (or damn near) is a tempo run. Since I relocated to a geographically endowed area this summer, these tempo runs are all hilly tempo runs. If I go for a long run, it's a long, hilly, tempo run. Therefore apply my advice with salt.
I'm now training with an older and wiser partner who's working hard to break me of old habits, but I'm an old dog...
The following is what I did in the weeks prior to this fall's marathon. I was shooting for about 2:38'ish (6:02 pace). Note I became injured shortly after the marathon. I now believe my training approach (all hard runs), creeping old age, and complete lack of stretching were all contributing factors. I was probably pretty lucky the injury didn't happen just before the race instead of shortly after. Neverthless, here's what I did, day by day, blow by blow:
beginning six and a half weeks out (where you were a few days ago):
18 miles @ 6:30 pace
5 @ 5:35 (local race)
12 @ 6:13
8.25 @ 6:06
5.1 @ 6:15
day off
20 @ 6:30
8.25 @ 6:21
7 @ 6:23
7.3 @ 6:04
6.1 @ 6:20
10.3 @ 6:20
15.25 @ 6:26
day off
8.6 @ 6:10
21.75 @ 6:19 (four weeks out, very close to eventual marathon race pace, although a bit off target race pace. This run felt fantastic.)
7.3 @ 6:19
5 @ 5:46 (felt like I was sprinting for five miles - this was way fast for a training run for me)
8.25 @ 6:16
7.4 @ 6:07
10.2 @ 6:25
day off
17 @ 6:18
5.25 @ 6:30
9.8 @ 6:18
9.8 @ 6:14
9.8 @ 6:10
day off
26.2 @ 6:33 (two weeks out, dry run of race course, felt like absolute hell afterward, but happy nevertheless to register a marathon - albeight in training - in under 3 hours)
day off
8.25 @ 6:22
8.25 @ 6.22
8.6 @ 6:19
9.8 @ 5:57 (scared myself with this one)
day off
12.1 @ 6:27
day off
9.5 @ 6:01
3.1 @ 7:25 (jog with my son)
8.25 @ 6:02
1.8 @ 7:00 (jog with my son)
6.1 @ 5:50
day off
26.2 @ 6:18 (race day)
I didn't set out to run any run slower or faster than any other - just as fast as I felt my body could *un*comfortably carry me over my intended distance. The variation in training pace probably reflects fatigue/overtraining as much as wind, heat/humidity etc. I also didn't have a specific schedule for daily mileage. I ran whatever felt right that day, with a weekly target of a bit over 60 in the back of my mind. Only exceptions were for planned long runs, when I generally got within +/- 2 miles of what I planned the previous week.
Looking back, maybe I got a bit stupid with my pace during the last week. Probably not a perfect taper. I've never been very good at arguing with myself and convincing myself of the wisdom of what I know to be true when endorphins are whispering something else. However, in spite of my training flaws, I believe the only reason I didn't hit my goal was the pace I took at the start, trying to keep up with the leaders who eventually also faded (although my fade was more pronounced and closer to the end when I was actually !%@#! leading... small field of course).
Anyway, to make this lengthy story shorter and get back to your specific question, I ran about 22 miles at near race pace about four weeks out. I don't think it hurt me, and I think it helped me somewhat (maybe not enough) to get my body familiar with a correct pace for race day.
Good luck and let us know how you make out!