Upgrading Firmware on ReadyNAS Pro Business Edition

The resync of the drives is going fine: upgraded the firmware to 4.2.20, and chose to simply expand the volume to take advantage of the 2Tbyte drives in all slots. I really, really like that.

Progress has been on 49% for about an hour now, and says it's going to take 162 then 252 then 56 hours to complete. Since my client will be back to work tomorrow and the team all bright and breezy and wanting to access their files, should I let them carry on as normal, or should I ask them to 'work locally' (we're very much a 1990s-style design agency ... ). Are lots of reads and writes during the resync likely to be problematic?

Also: I've just seen a pop-up telling me to reboot the device to continue with the update process, even though I'm at 50% now. Is this wrong - I'd have thought it not a good idea to reboot right now ... should I ignore that?

Thanks for all your input, once again. Mike