Good question fellas!
If you are adhering strictly to the ConDoc System, you would slice those elements and put the corresponding piece in each level. The Zorro extension is handy for this.
Regarding stairs, I tend to go heavy on the 2D graphics. There just isn’t a good way to section the stairs and net a clean 2D graphic. When you get to the top floor, you can use ONLY a 2D Graphic, no 3D Object, since there aren’t any more stairs going up on that level but you still need to show them. You can use this approach with any ELEMENT. So maybe you build columns on LEVEL 01 that reach through the entire building all the way to the top, but on the other levels just use a 2D Graphic.
On a recent project I put the downspouts on the ELEMENT_Trim layer within LEVEL 01. This layer only shows in section, perspective, and elevation so it really didn’t matter. It was slightly annoying to have them in the way at times, but probably not as annoying as slicing them all up, distributing to levels, then making as many changes as I did.
Let me know if that gets you back on track!