Of course it depends on different factors. I don't know if there is anything typical about rendering unless you use the same types of formulas all the time. I try to work them so I don't spend more than an hour or so with the main render. The ambient shadow, hard shadows and reflections/transparency can all add to the total time spent completing the piece. So sometimes I reduce the pixel size to cut the time down. Sometmies I want to show the detail more which will call for longer render times so I'll wait and do them overnight while I sleep or even during the day while at work. This piece took about an hour and the reflections render to a bit longer than that.