Hi Gafgar, have you set the Surfaces of the Block which one the Player doesnt see to "none"? This can increase the Build time much ! If made a Level with ~1500 Blocks, some time ago. This map had ~25000 Portals and the Build Time was 10 Minutes (VC + LC = High). And my PC is very old AMD Sempron 2500+ 512 DDR.
cYa Sebastian
Tutorials: [Blender]Terrain creation ENG/GER [Blender]Low Poly Tree Modeling [GIMP]Create a Texture for Terrains CLICK HERE