It is not unusual to use the Replace function multiple times to replace the same information. For instance, you may have a document that contains quite a few tabs. You can use the Replace function to replace two tabs with a single tab. In this way, you can get rid of the extra tabs. However, if your document contains many, many extra tabs, you can replace 8, 20, or 50 tabs with a single tab.
When you are specifying the number of tabs to replace, it is best to use a multiple of two. For instance, in the Find What box you would enter 4, 8, 16, or 32 tabs, and in the Replace With box you would enter a single tab. Continue selecting the Replace All button until you are informed the requested characters could not be found. Then divide the number of characters in the Find What box by two. Thus, if you had searched for 16 tabs, you would now search for 8. You will only have to click on the Replace All button once then. (Word could not find two groups of 8 in a row--if it did, it would have been replaced by the previous search for 16.) On the next iteration, use only 4, and finally 2 tabs. Basically, you have replaced all the extra tabs in around 4 or 5 operations. This is the fastest possible way to do the iterative search and replace.