If you plan to take your model to the analysis program, such as RAM. I think the way you did is correct. However, there will be some problems.
1. Your column line work will not be correct on the very top floor plan and floors that you change your columns' size.
2. If you are working with concrete, you have to join geometry every time you cut the section. (I think they solve this problem in RS2009.
I haven't got a chance to work with wall, but it should be the same way.