I think Poison mixed something up. The4d was talking about the map compiler. An improved Lite-C compiler will not help much here because the latter compiles the game-logic (scripts) but not the level geometry.

I once compiled a level for 3 days and the later version of the compiler is even slower now. Big levels are hard to make and you need serious optimizations and only low-poly blocky geometry. Even rotating some blocks slows the compiling process down.

What especially takes most time on your building process? Lighting calculation or Visibility or something else?