Yes. That's pretty normal for this kind of images. It's always a matter of quality. Some images look great with two hours some need even more than six. But I have to say, that Terragen 2 really doesn't have a fast renderer.. ^^
Well, I think they are right. Terragen is a nearly photorealistic renderer and I think the reflections should be Ok. Maybe the shadows are somehow mixed with the reflections, which can be confusing. But thanks for the Feedback.