> 1. How often will shutdowns happen with old SBS 2003 server if I turn it back on regularly?
> Every hour? Random time intervals?
Random time intervals of not less than 30 minutes but almost certainly not more than 8 hours. At least that was my experience.
> 2. As long as I can start it up, can I go ahead and complete the Microsoft migration checklist?
Yes, you can power the machine back up and continue with the process. The only problem is steps that take a long time COULD be problematic or even result in corruption if a shutdown occurs before they can complete.
> 3. Can I uninstall Exchange and demote the server but still keep it on the network?
> Microsoft's official word is no, but I'm looking to make it until Friday when the Line of
> Business application vendor will move the application to the new server. Can I use it
> as a member server without reinstalling the OS?
Not sure what migration method you're using, but if it's the MS migration documentation, then you have to uninstall Exchange and demote the server ANYWAY. But, that said, there's nothing you can do to get around the limitation - doing so would be violating licensing and we cannot help you violate licensing.
> 4. Because I am past the 21 day grace period, are there other problems that I should expect
> besides server shutdowns on the old server?
Out side of being in an unlicensed and unsupported state, no, no other problems.