Been assigned to help plan a Migration from Exchange 2010 to Exchange Online. We have several thousand mailboxes, approx 20K, wtih a limit of 1.5GB per box, so it will be a hybrid migration. I get how to set up the configurations and most of the pain points, but not I have not done a migration of this size and wondering about the length of time and effort to move? Is 1,000 users a week reasonable? Not sure of how hard it is to test and validate afterwards. I am just trying to get a general idea of what other have experience and how they have staffed project, so I can begin setting proper expectations.