I'm running my first marathon (Chicago) in October. I've been running for 14 years individually and on teams. Since high school, I have generally run about 8min./ mile pace for most training runs and so it feels more natural to me than any other pace. Based on recent 5k, 10k, and 10 mile race times, I have a marathon goal of 3:30 (most recent 10 mile race was just under 1:15:00, 10k in 43:40). I know that I should probably be running my long runs at around 8:45 or 9 minute pace and that is usually my intention but it rarely happens. I did 16 today and, much like my last 4 long runs of 12+ miles, I ran the first half between 8 and 8:15 and the second half in under 8 min pace with a pretty quick finish and energy to spare. My legs are a bit sore the rest of the day but I usually feel pretty good the next day for a 6 or 7 mile run and have had no problem doing my interval or tempo workouts three days after the long run. I've been running 4 days a week with one day of X-training.

My question is this: Is my long-run pace too fast or my goal time too slow? Because this is my first marathon, I'm not sure what I am capable of. Sometimes, my knees feel more achy when I slow down below an 8:30 pace. I'm reluctant to slow down my long run too much since my pace and recovery have felt comfortable so far but with my first 18 miler coming up in 2 weeks, I am wanting to be sure that I'm not setting myself up for overtraining or injury.

Any feedback would be helpful. Thanks!

I think what you want to make sure of is that you are building up your mileage at a very comfortable pace, and not focus too much on a specific pace. You should not be exhausted at the end of most of your runs - that's what will lead to overtraining.