For me, weekends are usually when I do my long runs. But lately I have been doing my long run earlier in the week like Tuesdays or Wednesdays between my morning and afternoon clients. I have been alternating between medium run (5ish miles) and then a long run the following week. I have been saving my weekends for tough track workouts, when I can use the local high school track.
At first, I was nervous that I would not be developing my aerobic capacity, but with the volume of runs, repeats, intervals, etc, the miles and conditioning are still developing.
A lot of runners may also feel that the miles would not be there unless there is a weekly long run, b ut I am still getting my miles. I am getting between 25-30 miles per week, which for me has left me feeling fresher and ready for the next run. The miles still come even with the amount of speedwork I have been doing.
For example my track workout today (program based on 25-30 miles per week for a couple middle distance events in May) was as follows:
15 minutes easy pace
8x 2 minutes hard with a 60 second jog recovery
4x 200 meters x 200 meters jog recovery (goal pace 49sec; 38, 39, 38,39sec)
15 more minutes easy pace
This gave me a total of 8.19 miles total. That is about what I would have run had I done my long run today. So you can see the miles are there. I am not suggesting you do this all the time, but I am just sharing what seems to be working for me. It might be worth a try even once in a while.