Recommendations or Experiences on Archiving Mailing Data
we have a custom overnight routine that copies data from civicrm_mailing_x and civicrm_mailing_event_x tables to duplicate tables with a archive namespace and then deletes the appropriate rows from the main tables. The biggest things is making sure that you adequately understand the relationships between the tables so you don't accidentally delete data that hasn't yet been archived due to a Foreign Key constraint. The other thing to note is that doing it this way means you loose stats from the reports etc for the mailings that have been archived.