Mac Forum / Applications / Excel / November 2006

I've been maintaining several mailing list files in Excel.  In part because
of different sources, in part because I'm nervous to have lots of data in any
one file.  

What is the collective wisdom on the number of full entries (ie, name,
organization, street, city, state, zip) that one can safely maintain in
Excel?  Of course, I'm backing up the multiple files periodically now.  I
talked to a mailing house that said that they'd worked with Excel files of
50,000 addresses.  True or crazy?  

Thanks!