Since my last post on this thread, I've had two Excel 2004 workbook files crash. One was 1.3Mb in size and the other 2.6Mb. The 1:2 size ratio may be only coincidental. These workbooks are constructed to perform different functions in support of different tasks. Both have multiple worksheets containing complex calculations with a lot of deliberate circular references that are extremely useful to what I'm doing. Both have forms that produce recipes for jobs to be performed in a laboratory environment over and over again with changed parameters for each job. When a new job recipe is made, a new form is generated while preserving all of the previous jobs that have been calculated. Comparing the workbooks that crashed, the 1.3Mb file has many more calculations than the 2.6Mb file, but I really can't estimate a ratio.
On the other hand, a third workbook file, 2.5Mb in size with over 5,200 rows of data, that caused me to start this thread has NOT crashed. It contains far fewer calculations than the other two and no reports or other printed versions are routinely made. I'll keep using it until it crashes just to see how big it can get while remaining functional. [Yes, I use both Time Machine and SuperDuper to make frequent backups to a TimeCapsule and two internal hard drives that are dedicated to backups.]
From the very helpful comments on this thread plus my own subsequent experiments, the answer to the question, "When is an Excel file getting too big?" seems to be, "It depends on how many calculations are involved."
In scrolling through this thread, it is apparent from my experimental results that every one of you who has contributed was correct and very helpful. I did the experiments so that I will know when to make a new copy of each workbook. The previous workbooks provide an archival record that helps to prevent "reinventing the wheel" on projects. Thanks again for your help. I love this forum. I am reporting back to you my results to confirm the facts that you gave good advice and that it was very helpful. Best regards.
