Jeffery,
The easiest answer to this is based upon your size and how many changes are made per day and whether you are using CUCM DRS or another way to back them up.
The company I work for currently makes about 10 changes a week, sometimes more, sometimes less. I back up everything twice a week. If I have to recover in this situation, making a few additional changes that occurred since the last back up is not a big deal. As far as what I back up, it is:
UCM,PLM,CDR_CAR, IM_and_Presence.
If you are doing this through DRS on CUCM, and you select UCM, it will back up the Publisher and all subscribers.
If you are doing it in another format, such as Pure or VMWare, then back up both if your subscriber is doing everything but the database. If your Publisher is doing everything (not best practices) then just back up the publisher.
