Pre-loading models

So when playing my game and checking the models, I notice that they make the game lag a lot, even if they are only in the line of sight far away rather than in the actual field of view (behind a wall, etc.). Is it possible to somehow reduce this lag, perhaps by reducing the level of detail drastically just a few metres ahead, or by letting the models be pre-rendered and then not automatically updated every second, like in Blender’s cinematics or similar. These objects are really kind of static, with no need to really load the backside of it or similar… any ideas?

At the beginning of the game in the first frame, attach the models to a node with disabled culling and then detach them again in the next frame. Also note that uploading the textures probably takes most time, so as always using a texture atlas helps a great deal.