Doorway detail done:
The only issue I see with this model is what is not seen: the other side. All my detail will be copied over. I can see the mirror being useful for the minor blemishes, but I would apply the y axis mirror for the larger ones.
I saved a copy of the door without any detail. I also saved a copy of the door with both mirrors on. Now I can go back however many steps I want and change the door at any stage of the process. Useful, I think, for smaller projects, but I could see it becoming over cumbersome for larger projects- at least if you save at every step of the way.