Workflow looks like your best bet. That way you use CV's scheduler to run it monthly.
The VADP and FS examples I linked in my earlier post indicate how you could restore using the command line, however you can replicate those by using the workflow objects in the Workflow. Create a Workflow String variable as a list (one for the files systems, the other for vadp), then use the ForEach control flow object to loop through. To do the date calculation you could sandwhich it into a couple Java lines as follows...
workflow.setVariable("date", (new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")).format(new Date((new Date()).getTime() - (20 * 86400000))));