Since we don't have that many clusters, we still do ours by hand, so, in that sense, I have nothing to help you with here (You're welcome!) other than to say I'd probably write something in `expect` to do it.
Though, for the paranoia level of 'every 30 days' demonstrates, there's probably a lot of changes you'd want to do.
* change admin's password
* audit the allowed keys against an external key repo
* change diag's password
* change DFM/oncommand's password
* change VSC's password (if applicable)
* change the cluster switch passwords