Just checked: the render is now at frame 163 out of 192. For some reason what should be the easy frames take way longer that the complex ones. I think I have a fix, but I am letting the current render run for another day. Total render time will by then be four days. Resulting screen time: 8 seconds. At this pace I will surely finish the animation by the Dutch holiday "Sint Juttemis". Optimize I must! Yeah, yeah, I said that before.
Update : Finished today, hurray! Too bad I do not have the next scene ready to render yet. Close though.