If you notice that all of a sudden the DXP file size has increased, double check all data tables/source to make sure they are still linked to the source.  Usually if the file size jumps, it is because a data table has become embedded, and now the data is being stored in the file.  This can be checked by going to the Edit > Data Table properties dialog.  Click on one table at a time, and make sure the radio button in the General tab is set to "Lined to source" and not "Embedded".  If the data table is embedded, it needs to be replaced and reconnected.