We're 7 weeks out from Chicago, which leaves 5 weekends for quality long runs, assuming that a week out you do about 13 miles steady. (September 9/10, 16/17, 23/24, 30/1 Oct, October 7/8, 14/15).
It all depends on what you consider a "really long run," but I would say up to 2:30 is a long run, 2:30-3:00 hours is in-between, and over 3:00 is for most purposes a really long run. With 7 weeks to go, you need specific marathon pace work, not really long easy runs. IMHO.
If you're comfortable with the distance of the long runs I would try and use the next 5 weeks to get in at least 3, perhaps 4, long runs with some tempo and marathon pace running in them, and on the intermediate weekends do a steady long run that is shorter than you have been doing.
September 9/10: 2:20. Warm-up for 15 minutes. 30 minutes at marathon pace. Hour easy. 20 minutes at marathon pace. 15 minute cooldown. (Or more if you feel energetic)
Sept 16/17: 2:30-40 steady
Sept 23/24: Warmup for 20-30. 3-4 x 20 minutes at marathon pace with 2-4 minutes between. 20-30 cooldown.
Sept 30/Oct 1: Easy running for an hour. 50 minutes at marathon pace. 15-25 cooldown. Or 2:20-2:30 steady if you want a break from the faster long runs.
Oct 7/8: Easy for 35-40 minutes. 20 minutes at tempo. Easy for 35-40 minutes. 20 minutes at tempo. 15-20 minutes cooldown.
Oct 14/15: 90-100 minutes easy.
If you do these kinds of long runs you shouldn't do more than one other workout the rest of the week. The long marathon pace stuff can wear you down subtly, so be sure to run on the easy side of normal on other days of the week.