Everything you do should have a reason. Doubling is fine, so long as you aren't doubling for the sake of doubling. It has its time and place, but shouldn't be a main focus of your running.
So why are you doubling so much? Do you get fatigued from 80 mpw in singles? Is it a time issue?
I've dropped from 16:00 to 14:45 over the last 10 years, and I've done mileage both ways: Only singles and lots of doubles. In my opinion, the sweet spot is somewhere in between. As a general rule, you should have one run a day of 60 minutes, and your doubles shouldn't be less than 30 minutes. Doubles are great the day after workouts, it will help you recover faster. Or the day before, to allow for more mileage without fatiguing your legs. But otherwise you don't need it.
A run of 12-15 miles is good in the base phase, but once you begin serious workouts, more than 12 miles is unnecessary.
My base phase this last year went something like this:
Mon: 8 mi
Tue: 12 mi including short hill repeats
Wed: 10 mi
Thu: 12 mi
Fri: 12 mi including some kind of tempo work later in the phase
Sat: 10 mi
Sun: 16 mi
Total: 80 mi. No doubles, but they could have been added Tue/Thu if I'd needed
Later, when I got into workouts:
Mon: 13 mi, track session
Tue: AM 4 mi; PM 6 mi
Wed: 13 mi, track session
Thu: AM 4 mi; PM 8 mi
Fri: AM 4 mi; PM 6 mi
Sat: 12 mi, track session
Sun: 10 easy
Total: 80 mi. 3 days of doubles, 2 of which broke the 60 min run rule, but the focus here was on the track sessions.