I ran sub 17 last year on the following schedule at 39 years old. Started running a year and a half before that.
monday 3 wu, 5-6 mile tempo, 1-2 cooldown
wed 3 wu, intervals (200,400,or800) 3 cooldown
sat 5 wu, 5k race, 3 cooldown
Some weeks I would add a steady 10 mile run.
You will be a lot better off running 3 days of 10 miles a day rather than 5 or 6 days of shorter mileage. It will also save you time as well. I even ran a 1:19 half marathon at the end of the summer after having not run over 10 miles at one time the whole year.
The only problem is that you will peak after a few weeks and not be able to run much faster, but it will allow you to be very competitive and enjoy the sport.