That depends on the speed of the connection with Internet on the several locations from which you download concurrently, and the speed of the various storage lockers sites, and the speed of moving the results to one of the many computers to combine all part on that one.
So, since this seems to be a one-time problem, I'd just start all downloads concurrently at the end of the evening and expect everything to be ready next morning when I wake up.

Kees