My base concept is a 3-stage logarithm of 10. That is, the polygon count increases tenfold every three steps higher. For simplicity, I'm using simpler numbers. The polygon count always will start with 1, 2, or 5 and end in from 1 to 5 zeros (100,000 is the highest, 200,000, requiring over 100,000 vertices, will not work with MED as the mesh doesn't get saved properly (DirectX limitation)). Now to take out my experimental level (a level that contains just one small block (default texture and invisible), a position, and all test subjects, duplicates in particular.
Experiments are a great way to optimize something. This way, you can find the peak performance for your game and learn better techniques to optimizing. You always need a base to branch off from (the control as it's called). From there, you provide variations.