Other machines just borrow the license on the virtual network. One also makes a great Rockwell license server. Whole virtual machine (Empty install) only takes about 21G of drive space. You can also turn off the automatic update. They are great machines because you can test everything Windows 10 without all the bloat that comes with the regular version. I also bought several Windows 10 LTSC licenses ($4 each on eBay). That feature has been a big lifesaver, especially with Rockwell fatware. Not sure if a new software is going to hose your machine, just take a snapshot and if it does, revert back and it's back to exactly where you took the snapshot. I even have a couple of Linux machines for test web apps.
It's also been great for testing new versions of server and Windows. More information can be found in the AB publication LGEM5K. The goal is to mimic the function of a PLC without the actual hardware and thus do advanced debugging. Then I have setup a virtual network that connects them all, even if I don't have a network connected. RSLogix Emulator 5000 is a software simulator for the Allen Bradley line of Logix 5000 controllers (ControlLogix, CompactLogix, FlexLogix, SoftLogix5800 and DriveLogix). I can open multiple machines on three separate monitors.