I just created a simple test with one of my own test models, without doing anything special and it stayed exactly where I put it. I used "Object/Add entity..." to insert my model, because it is not static (has animation). I don't know if "Add model..." has a different affect; I didn't try this.

Using "Build BSP Map" on small test levels does not take a lot of time. Regardless, it needs to be used at least once. After that, you can use the alternative options; 'Update lights", if you changed or added lights, "Update entities", if you changed, updated, deleted entities. I believe "Simple map" is used to create map entities... static prefabs, for instance, that don't required modelling in MED.