Is that on a regular stationary bike? (Pretty hard to be as efficient on those as on a spinner).. If so, I'd say that's doing a pretty good job. Not too beginnerish at all. Before I started spinning, I rode one of those after taking a few weeks off (just walking) b/c of an injury. I felt like I was working so hard, but my HR was only in the low 140s if that, and I was at about 11mph. I'd consider myself cardiovascularly pretty fit but not at all in biking shape at that point.
A "long" ride on a spinner depends on what kind of workout you're doing. It seems to take me forever to warmup, so the first 30-45 min is torture. But after that, I can spend 2 hrs easy. Higher intensity intervals tire me out faster than endurance or steady state taining of course. An hour isn't a long time on an indoor bike but it's sufficient for general fitness I think, especially if you warm up faster than me.