Depends what you set the shadowmap light settings to.

0.01shadow map bias, 4096 map = 6-12 hours just to render the map. Then the render starts..
1.00 shadow map bias, 256 map = a few seconds ...

Just an example. Not hard fact

On the other hand,,, if you are using below Poser6sr3, you may have locked up in an infinite loop and you'll be rendering a map next month. P6sr3 should let you cancel.