I'm still confused. you don't have the DRL's in the rear. But do you have standard tail lights? When you flips the lights all the way on, do you have tail lights? If so, shouldn't be an issue.
Personally, I drive with my headlights on every single time I drive. It draws almost nothing, is safer, and in a Subaru, they automatically shut off when the car is off. Why wouldn't you have your headlights on all the time?