I'm putting together a project to upgrade a large organization's Exchange Server 2003 to 2010. The project has all new servers to house the new Exchange Server setup. The project calls for 8 weeks, but I don't feel like it should take that long. I know there are a few considerations like getting certificates created by the other team members, submitting rules to the firewall, and basic configuration settings, but should it take that long? They have very large DBs for the mailboxes, but they can probably be moved and done over a long weekend.
In short, since Exchange 2010 is going on all new boxes, will it take very long to go through the whole process? Even the co-existence shouldn't last too long, right?