Here is a little tips to delete all previous meeting automatically (due to a scheduled task) :
#Calculating J-1 date
$ddate=get-date -uformat %m/%d/%Y
#Adding rights on the mailbox (do it Once)
Get-Mailbox “application.mailbox” | Add-MailboxPermission -User $localu -AccessRights Fullaccess -InheritanceType all
#Deleting old meeting/mails
Get-Mailbox “application.mailbox” | Export-Mailbox -EndDate $ddate -DeleteContent
That could be really… really usefull !