Long runs are a workout, and should be viewed through that lens (ie, an easier day before and a recovery day after). They can be done progressively based on feel, or it can be done at a consistent, fairly easy effort level with short periods of acceleration to break up the slog and reset your form (essentially, almost like doing a few striders mid-run). I would definitely monitor pace though, as it's really easy to let the pace slide down a couple notches when you've been going for a while and are feeling good.
One thing I'd like to note is that "moderate miles" have little value in an overall training regimen. The point of non-workout mileage is to build and maintain an aerobic base and to recover from workouts. From what I've seen, most people (past-me included) that do mileage at a moderate pace are actual doing what essentially amounts to easy tempos, which are insufficient for recovery. I believe Tinman's easy measure for recovery pace is one's date 5k pace plus 2 minutes is the fastest they should be running. Not trying to tell you what to do , just providing some food for thought.