Office 365 - Archiving Mailbox Procedure

Hi,

If your organizations policy is to retain a copy of a former staff member's mailbox, what is your procedure in doing so?  Do you move the mailbox data over to their replacement?  Keep the email account going, but disable it for a specified period of time?

We perform a combination of the above.  I also started to archive pst files prior to deleting the account(s).  This process is time intensive, and I was hoping to find a better solution.  Any suggestions? 

Thanks!
Chris