I understand running Paces in your workouts. You have goals to hit, and you need to hit your paces.
But, on your easy/recovery runs, why doesn't EVERYONE use a Heart Rate Monitor? It is a much better gauge of what is "easy". Your Heart will know if you haven't been getting enough sleep, or if you have a virus that hasn't set in yet, or if the weather is getting to you, etc.
Just find your max HR, set a 70-75% ceiling for your HR, and off ya go.