It's been going for about fifty minutes so far via the Thunderbolt cable. We're doing it from the backup drive because my old computer crashed three times in a row and was not reliable - and if we'd tried to do it wirelessly it would have taken at least twelve hours, if not more. It says fifty-four more minutes, but I think once it gets past the big files it's doing, that could go faster. That's happened consistently since we began.