Thank you all for the help! I was looking for the timer setting (default 2 hours) and found that with the assistance given here.
The rest seemed self explanatory. Iray tries to add in things not in the render for shadows and reflections that might affect the target image from off screen. All this has to be loaded and processed, so it adversely effects performance.
Are you referring to that individual materials settings? Or the focus on the render settings itself? (I know photography, so the latter is self explanatory)