How do you know when virus def folder is in poor maintenance?

In studying Smart Definitions I found the following previous post:

 

Note: NIS has always performed automatic-housekeeping for the virusdefs folder structure. Thus there is no disk-storage penalty for the use of virus-defsets over time. In some circumstances, errors in the NIS installation process or file-access-permission errors (usually the delete-file permission in the NIS virusdefs folder structure is lost due to improper shutdown or a power-failure at precisely the wrong moment) allow old virusdef versions to "pile up". This is not a normal occurrence. Finding poor NIS virusdefs-folder-maintenance and lots and lots of obsolete virusdef versions is a valid reason to perform a NIS remove/run-NRT/reinstall process.

 


Questions please:

 

On the last part,

 

" Finding poor NIS virusdefs-folder-maintenance and lots and lots of obsolete virusdef versions is a valid reason to perform a NIS remove/run-NRT/reinstall process",  

 

how do you know when you reach that point? Virus defs folder in poor maintenance and obsolete virus defs?