>> I normally interrupt by hitting abort just once
> Don't kill it. pause it and resume later.
> Hibernate the PC if you must but don't shut down.

Thanks - I'll try to do that whenever feasible.  I am not always running on
the same computer, however: I have this USB external hard drive which has both
the program and the mirrors on it, which I attach to other peoples'
computers.

(Of course now I have the command line version running, so I assume there is
no way to pause it, or even to interrupt it gracefully - or is there?  I
gather using the command line version was a less felicitous idea..)