In my experience, typical render times are whatever can get finished overnight. So up to 8 hours or so on average. Many complicated renders will take much, much

In my experience, typical render times are whatever can get finished overnight. So up to 8 hours or so on average. Many complicated renders will take much, much longer. And then of course many simple things like previews and non-final renders go significantly faster. It varies widely depending in the complexity of geometry and lighting model. Blinns law is completely true. The limiting factor on render times is the impatience and work schedule of the people submitting the jobs.