So here's the big question: Do you enjoy running on trails as much as I do? I was thinking about that all day today. What is it about running off road that makes it so pleasant and exciting? Like running this cross country course yesterday.
As you can see, there are trees everywhere pumping out oxygen (not CO2 as you find in the cities and highways). Also, there's evidence that being in such relaxing surroundings reduces stress and may trigger certain biological responses such as lower blood pressure and the production of serotonin. Most importantly, each foot placement is different so you're building stronger connective tissues in your feet, ankles, knees, and hips, thus avoiding repetitive stresses associated with running on hard, even surfaces.
Ultimately, though, it's way more fun to run in nature, ignore your pace, and just exercise for the joy of running like you did when you were a kid. I'm discovering so many trails around where I live as a result of not focusing exclusively on pace or distance. Yesterday I even ran across a very waterlogged field without any problems. I honestly never gave it a single thought.
One tip: Make sure you have the right shoes for this. Look for something with grip that isn't too aggressive or something that is marketed for light trails. You want to get a bit of a grip but you don't want to wear out the lugs when you run on the roads. My Lone Peak 5s work just fine!