I have just checked, the preferences are user specific.
So, if you create another user account on your pc, you can create another set of preferences on the same machine. You need to unlock the maps again for the new user, you can do this on as many MapSource installs as you like, because the lock applies to the GPS, not the pc software.
User switching also works, so you can be running MapSource twice (or more) with different routing preferences set and just switch users (rather than logging off) to access them. You can also upload routes etc with both users logged on, because the 2610 is available all the time and is detected by each MapSource session.
The only downside is that you can't copy/paste between users.
You could therefore have as many sets of preferences as you liked, each under its own user account. You could create multiple versions of the same routes just by opening the same file in the relevent set of preferences and recalculating them.. A-B avoiding motorways, with additional vias, quickest, shortest etc.
Has to be better than running two machines!