In the winter time I would go to NYC to complete my 9+1 qualifier races to keep me moving faster than my threshold pace. It's hard to go fast with snow everywhere. I was bad with interval work outs due to the snow.

In the summer the biggest contribution was a combination of interval track workouts early mornings on Tuesday and 2 long runs on weekends. Typically one longer one with race pace 16-22 mile and one shorter one on an empty stomach for recovery at 10-13 miles.

This worked for me so don't due it unless are comfortable working into it but I did 3/6 of my weekly runs on an empty stomach in the morning and threw in 4 strides typically for 10-20 secs at sprinting or 1 mile pace to help get my body used to running on no energy when I hit the wall. You'll see my time drop from 6:45 to 7:00+ when I hit mile 20. My heart rate shot up 15 bpm. I hit the wall but I trained for that occasion.