Let me ask you another question. Why do you want to break the model down. Is it just for the purposes of viewing the model isolated one floor at a time, or do you need to physically have a separate file for each floor that you need then then make changes to.
If it is just a viewing issue then I would use section cuts. If you make a to level section cut you can cut for example at the top of the third floor. If you also want to cut at the bottom of the third floor (or top of second floor at the same time) then you can put everything at the top level into a group, now enter that group and make your second section cut. Now you can save that as a scene and do the same thing for all of your floors. When you get an updated model next week you can drop it right in place of this (very easy if you make your model a component, then you can reload from another file). You won't have to re-create the section cuts or scenes every week, ready to view as soon as you bring in your new model.
