Marathon Training -- Week 4

I don't know if it's that I'm just fitter or not holding back due to an injured foot this time around, but I'm training at about a minute per mile faster than I did two years ago. I'm beating up my legs pretty good. My feet feel fine. I've gone back and looked at my early marathon training of two years ago and noticed a pattern of nagging aches and pains in my left knee and right shin. I also struggled with a sore right hip. After about 6 weeks of training, all of these issues worked themselves out. I don't have any of those this time around, hence my beating up on my legs a bit more than I probably should. I want to be stronger in the last four miles of this marathon. My pace dropped off two and a half minutes after 22 miles of my first marathon. I don't want that to happen in SF. I want to run an even-paced marathon. I don't know if it's going to be in sensible pacing or preparing my legs for the last few miles that will allow me to do this. I have to figure this out.