I usually look for the flattest route to run, and even that has a 6m elevation! Though my pace is considerably slower than yours! My fastest hill split yesterday was 7.39 min/km. I am aiming to do hill running, so I will start using some of the steeper hills soon, building up gradually.
Hills give you an extra workout to build strength. I am trying to vary my runs a bit more. There is no overall plan, but mixing it up ought to be good.