I'm on my way with animating the blood vessel tunnel. Where I have sets of six blood cells running on a track over. Despite the complex mirroring and the number of polygons, this frame took 2 minutes 36 seconds to render at 50% resolution and quality.
However as shown by the outliner this scene is quite cluttered with overlapping EP curves which I figure I can remove and have the attached blood cells attached to one set of EP curves, The cells are also quite jittery which is something I will also need to fix. This might as well be a rework though.
My plan is that once these blood cells reach the end they will switch into lower-res models in order to save processing time.