The actual rendering time (time the Iray server takes to render your scene/project) is a function of the render parameters set in the Render Settings Tab, specifically:
Max samples (higher max samples increases render time)
Number of Frames (higher number of frames increase render time)
Because every project is unique in its design and complexity, it is almost impossible for us to calculate a reliable render time.
However, it’s helpful to note that the longest total time (upload + render) is always the first time for a scene or project.