He's very young... will be two in January.
Lunging - I've attempted to lightly lunge him before, in the round pen, and have noticed that it doesn't take long before he's licking and chewing to come back. Within a circuit or two (at a fast jog), he's asking to come to the center. He does this when free lunged and while attached to a line. He's a very submissive horse by nature and very intelligent. I'm a little hesitant to lunge him in the field though, because it is a natural field and full of rocks, hills and dips. It's great for the horses because they learn where to put their feet and are very sure-footed trail mounts as a result, but I don't know if it's the best place to lunge a horse. There are small areas that are safe to lunge, but those are few and far between in the field. Am I being too over-protective or wary? Is there a safer option that would render the same results, or should I try to lunge him carefully and allow him to pick his own footing while I work him long enough to induce some sweat?