Yeah this software also does this
http://www.guidingtech.com/653/winmend-automatic-shutdown-log-off/
So you are suggesting I just manually start the downloads with a FTP or Download Manager and make the software turn off my PC after a certain number of hours ?
That would not help because of two things.
1) I might be away or asleep at the time I want my downloads to start.
3) The downloaded files might get corrupted if the PC shuts down / switches to sleep while the download is in progress. I know the software rolls back a certain amount of bytes once you resume the download to prevent that... but still.