First of all, you have to differentiate between engine LOD and managed entities. The first thing is really easy: you setup LOD stages for you models and the engine switches between them (geometric detail) to save polygons and power for a deep view perspective. A6 supports 4 LOD levels (which is enough). So when you want to let your models disappear after the second LOD stage, just leave out 3rd and 4th LOD stage models. Engine LOD is always faster than LOD management you are doing by yourself. Though, its not that nice.. if a model turns into a zero-mesh, it is just clipped away (no fade or something similar).

Managed entities are totally different and can be easily combined with the LOD management. Imagine you have a wide outdoor level with a really high amount of entities. Trees, bushes, stones, rocks, whatever.. very repeatative stuff patterend all over the map. So, let us say you see 18 trees, 20 bushes, 20 rocks and 100 grass sprites _averagely_ all the time. You could save all positions, rotations, scales, etc. of all tree, rock, bush and grass entities all over the level. Then, during runtime, none of those entities are loaded.. only 18 tress, 20 bushes.. and so on. What you are doing: while wandering through the map your entity manager checks the camera position and view to check whcih virtual trees for instance are "viewable" but arent "there". So you take one tree out of your list, which isnt used or far away and move that tree to that position. The performance benefits from the constant entity rate and saved ent_create isntructions. This method in combination with LOD is it worth to check it out. I guess, that its only worth when having a WIDE landscape or whatever level populated with very similar objects.