True, but it depends what you are doing. As @Roger Kallberg mentions, it is very helpful migrating a selected set of users. Another thing is that the voicemail database changes more then the configuration database does in CUCM. What I would do when migrating the entire system was to build the new system on the target version with the user configs, but not bring over the voicemail messages. That would mean a system ready to receive messages at cutover time, and I could just change the destination for the appropriate route patterns to the SIP integration. Then I could run another COBRAS export after the existing system was no longer active including the messages, and import that over top of the new system. That would get messages and last minute config changes like password and greetings the users had done at the last minute. I did always try to NOT bring over the messages since saved ones reappear as new when you migrate them which can confuse the user. If you leave the old system accessible for a while via a different destination #, the users could get to old messages for a while.
Everything you have said about the newer methods is totally valid @Nithin Eluvathingal , but I have used the methods I described for years so I am still comfortable doing it that way. Old dogs and new tricks, I guess!
