How long should Firmware update take??

I'm migrating from an Ultra 6 to a Pro 6, and I'm updating the firmware on the Pro 6 to the latest version.

Everything seemed to be going fine but after rebooting, the Pro 6 LED screen has been stuck on "Booting... Updating FW" for at least half an hour now.

I know it's critical to allow FW updates to complete, but I have no way of knowing if the update is still in process or if it's frozen up and failed. I've never seen a firmware update take this long, but I don't want to interrupt it.

I've installed my 6 disks from the Ultra into the Pro already (apparently it needs disks in it in order to Setup/Configure), so I'm hoping that's not part of the problem.

If the update has failed, what's the best way to proceed? Power cycle the Pro 6 and hope that it comes back, and try updating the FW again?

Thanks,
R