Friday morning is often my favorite day to run. I only have about 90 minutes to spare, which gives me enough time to run 8 miles. Saturday and Sunday, however, I have enough time to run 15 to 18 miles, so I get to take long runs. 

There is also less traffic those mornings, so I have almost no delays at stoplights. Consider that since I run roughly 32 miles between Tuesday and Friday, and between 30 to 36 miles  on Saturday and Sunday I run a longer distance on the weekend than I do during the week.