That's a good start for a tree Tim. Next time scale the canopy larger and raise it higher above the base group. My landscape scene took 9hrs 40min to render (1600x900), so it's all about how you set it up. 1 hr for one tree seems a bit too long to me.
Robert, the leaves probably wouldn't get milled, since it's not geometry. The model, I assume, gets exported to a different format.