Thank you William. That's very helpful.

On the issue of running multiple instances of HTTrack, both using the same
HTTrack project, I actually happened to somehow accidentally do that
yesterday. 

When I discovered the error, both instances were running fine. However, upon
canceling one, and then canceling the other after the first one was fully
complete, it seems (I'm not 100% sure) that I lost ALL data downloaded from
both of those two instances. (Not the whole project, just the update.)

What exactly is HTTrack doing when you give it two instances of the same
project to run, and what would cause the two to cancel themselves out. (Again,
I may be mistaken in what actually happened.)