Seems a bit of time is waisted when someone makes a comment on reviews older than 30 days. A moderator has to ask not to comment on reviews older...
It does seem that it would be fairly easy to lock reviews after the 30 day mark programmatically. A bit of code added to permissions possibly.
I use to know how to do this stuff but once you get over 50 everyone expects you to get a phone with easy to read numbers it seems.