Shared Services Audit Purge Days

Reviewing the documentation, it notes that when enabling Shared Services Auditing that data is, by default, purged after 25 days and gives instructions for updating. 

My question is why is this period so short? I would like to be able to record much longer periods of time for audit purposes.  Would there be system limitations to setting this to 180 or 365 days? Note that this system provisioning is not changed often and has less than 25 users overall.