I am getting ready to migrate my student population from Exchange 2007 to Exchange 2013 (about 7000 mailboxes). I have already migrated 1500 employee & resource mailboxes to Exchange 2013 and all is working well. The employee move planned over a 3 day weekend, but actually took over 5 days. To avoid this on the student move, my plan is to start batch migrating mailboxes, but not completing the move, several weeks in advance of our actual migration start date, then complete the migration during the actual migration window. Has anyone completed a migration move in this manner? Any drawbacks with doing it this way? I have not found much online about this type of migration.
Thanks!