Thank you both for the inputs. I'll see if they work. Obviously larger files will slow the computer's execution. However, there's no good reason why my plan should be so large, especially in light of David's experience. My previous version of this software did the same: slowed over time to the point that it was unusable. It's as though the software never removes any details, but simply overwrites them and increases the file size.
My Suite 2009 has slowed to the point that executing any command takes multiple, double-digit seconds and my "dream house" file size has ballooned to 188Mb. I don't import any imagery other than the architectural fixtures resident in the software's library. I'm running it on an HP TouchSmart 610, Win 7, i5-2400, 3.10GHz, 8Gb RAM, 64-bit processing. The situation has reached the point where I no longer enjoy using the program. Advice?