Question:
Can I run a program/process/rule to prune the sent items and/or deleted items folder for users?
Answer:
You could use either ExMerge or Mailbox Manager to do that. ExMerge will let you specify which folders (and even which mailboxes) to use and then specify criteria for which messages you want to remove (such as date range).
I haven’t used Mailbox Manager myself, yet, but I understand it has similar capabilities.