When it comes time to do an Enterprise Vault migration there are many different options available to you and your company. Rather than trying to figure out the best on your own, get some expert help. One such way is to attend the upcoming Webinar from Adept-tec. Look for more details here:
http://www.symantec.com/connect/events/enterprise-vault-deep-dive-tools-moving-archives
Maybe you're already an expert?
It doesn't hurt to spend an hour on a *free* webinar listening to some other options which might be available to you and your organisation.