Rendering performance, preparing scene data

Following unique setup:

I imported a map in blender using my self-written python import script. I want to use blender to render cubemap sides which I can then pack into the map.
The cubemap images are really really small (128x128 and lower). I am using blender internal, and disabled shadows, ss, environment mapping and raytracing.
The render itself is really really fast (1 second per cubemap side), but for each image it hangs on “preparing scene data” for 20 seconds. I already put the scene into an animation in the hopes to speed things up (the animation being the camera teleporting around to the different spots and rotating to all 6 cube sides, but with no avail.
I’m not sure what is happening at this part, and the thing is that the scene itself never changes. Everything in the scene stays the same except for the camera.

I’m really thankful for any advice on how to cut this down. Bare render times for one cubemap are 6 seconds, with the scene preparation that happens over and over again its 3 minutes.