I've got the same sort of loop that I ride — actually two variations of the same thing: a 13 mile version and an 18 mile route that encompasses the same 13 mile route but with a 5 mile extension. I ride them often and use the data to gauge my training. For me, I keep an eye on average speed which should increase over the course of the season. I have the Garmin 520 set to break down my rides by mile so I can geek out on each segment of the ride including a couple of big-a** hills.