You might also try varying your running. Try fartleks, or hill repeats, to go along with your long, steady run. I did this last spring/early summer, and knocked off 1 minute per mile in just a couple of months. Then I got caught up in distance, but I will be returning to this variety soon. I think it speeds up the progress. Just like in weights: it's good to mix up really heavy, deliberate stuff with lighter, higher rep circuit training once in a while. Spice is the variety of food.